Peritoneal dialysis systems employing a liquid distribution and pumping cassette that emulates gravity flow

ABSTRACT

Peritoneal dialysis systems apply fluid pressure to move liquid. The systems can emulate either a fixed head height condition or different head height conditions, independent of the actual head height differential between the patient&#39;s peritoneal cavity and the external liquid source or destination. The systems can also switch between low-relative pressure flow mode when considerations of patient comfort and safety predominate and a high-relative pressure flow mode when considerations of processing speed predominate.

FIELD OF THE INVENTION

This invention relates to systems and methods for performing peritonealdialysis.

BACKGROUND OF THE INVENTION

Peritoneal Dialysis (PD) periodically infuses sterile aqueous solutioninto the peritoneal cavity. This solution is called peritoneal dialysissolution, or dialysate. Diffusion and osmosis exchanges take placebetween the solution and the bloodstream across the natural bodymembranes. These exchanges remove the waste products that the kidneysnormally excrete. The waste products typically consist of solutes likesodium and chloride ions, and the other compounds normally excretedthrough the kidneys like urea, creatinine, and water. The diffusion ofwater across the peritoneal membrane during dialysis is calledultrafiltration.

Conventional peritoneal dialysis solutions include dextrose inconcentrations sufficient to generate the necessary osmotic pressure toremove water from the patient through ultrafiltration.

Continuous Ambulatory Peritoneal Dialysis (CAPD) is a popular form ofPD. A patient performs CAPD manually about four times a day. DuringCAPD, the patient drains spent peritoneal dialysis solution from his/herperitoneal cavity. The patient then infuses fresh peritoneal dialysissolution into his/her peritoneal cavity. This drain and fill procedureusually takes about 1 hour.

Automated Peritoneal Dialysis (APD) is another popular form of PD. APDuses a machine, called a cycler, to automatically infuse, dwell, anddrain peritoneal dialysis solution to and from the patient's peritonealcavity. APD is particularly attractive to a PD patient, because it canbe performed at night while the patient is asleep. This frees thepatient from the day-to-day demands of CAPD during his/her waking andworking hours.

The APD sequence typically last for several hours. It often begins withan initial drain cycle to empty the peritoneal cavity of spentdialysate. The APD sequence then proceeds through a succession of fill,dwell, and drain phases that follow one after the other. Eachfill/dwell/drain sequence is called a cycle.

During the fill phase, the cycler transfers a predetermined volume offresh, warmed dialysate into the peritoneal cavity of the patient. Thedialysate remains (or "dwells") within the peritoneal cavity for a time.This is called the dwell phase. During the drain phase, the cyclerremoves the spent dialysate from the peritoneal cavity.

The number of fill/dwell/drain cycles that are required during a givenAPD session depends upon the total volume of dialysate prescribed forthe patient's APD regime.

APD can be and is practiced in different ways.

Continuous Cycling Peritoneal Dialysis (CCPD) is one commonly used APDmodality. During each fill/dwell/drain phase of CCPD, the cycler infusesa prescribed volume of dialysate. After a prescribed dwell period, thecycler completely drains this liquid volume from the patient, leavingthe peritoneal cavity empty, or "dry." Typically, CCPD employs 6fill/dwell/drain cycles to achieve a prescribed therapy volume.

After the last prescribed fill/dwell/drain cycle in CCPD, the cyclerinfuses a final fill volume. The final fill volume dwells in the patientthrough the day. It is drained at the outset of the next CCPD session inthe evening. The final fill volume can contain a different concentrationof dextrose than the fill volume of the successive CCPD fill/dwell/drainfill cycles the cycler provides.

Intermittent Peritoneal Dialysis (IPD) is another APD modality. IPD istypically used in acute situations, when a patient suddenly entersdialysis therapy. IPD can also be used when a patient requires PD, butcannot undertake the responsibilities of CAPD or otherwise do it athome.

Like CCPD, IPD involves a series of fill/dwell/drain cycles. The cyclesin IPD are typically closer in time than in CCPD. In addition, unlikeCCPD, IPD does not include a final fill phase. In IPD, the patient'speritoneal cavity is left free of dialysate (or "dry") in between APDtherapy sessions.

Tidal Peritoneal Dialysis (TPD) is another APD modality. Like CCPD, TPDincludes a series of fill/dwell/drain cycles. Unlike CCPD, TPD does notcompletely drain dialysate from the peritoneal cavity during each drainphase. Instead, TPD establishes a base volume during the first fillphase and drains only a portion of this volume during the first drainphase. Subsequent fill/dwell/drain cycles infuse then drain areplacement volume on top of the base volume, except for the last drainphase. The last drain phase removes all dialysate from the peritonealcavity.

There is a variation of TPD that includes cycles during which thepatient is completely drained and infused with a new full base volume ofdialysis.

TPD can include a final fill cycle, like CCPD. Alternatively, TPD canavoid the final fill cycle, like IPD.

APD offers flexibility and quality of life enhancements to a personrequiring dialysis. APD can free the patient from the fatigue andinconvenience that the day to day practice of CAPD represents to someindividuals. APD can give back to the patient his or her waking andworking hours free of the need to conduct dialysis exchanges.

Still, the complexity and size of past machines and associateddisposables for various APD modalities have dampened widespread patientacceptance of APD as an alternative to manual peritoneal dialysismethods.

SUMMARY OF THE INVENTION

The invention provides improved systems and methods for performingperitoneal dialysis.

According to one aspect of the invention, the improved systems andmethods serve to establish flow communication with the patient'speritoneal cavity through a pumping mechanism that comprises a pumpchamber and a diaphragm. The systems and methods emulate a selectedgravity flow condition by applying fluid pressure to the diaphragm tooperate the pump chamber to either move dialysis solution from theperitoneal cavity or move dialysis solution into the peritoneal cavity.

Systems and methods that incorporate this aspect of the invention canemulate either a fixed head height condition or different head heightconditions. The systems and methods are able to emulate a selected headheight differential regardless of the actual head height differentialexisting between the patient's peritoneal cavity and the external liquidsource or destination.

According to another aspect of the invention, different fluid pressuremodes can be used to operate the pumping mechanism. The improved systemsand methods can rapidly switch during a given peritoneal dialysisprocedure between a low-relative pressure mode and a high-relativepressure mode. The low-relative pressure mode is selected during patientinfusion and drain phases, when considerations of patient comfort andsafety predominate. The high-relative pressure mode is selected duringtransfers of liquid from supply bags to the heater bag, whenconsiderations of processing speed predominate.

In a preferred embodiment, the systems and methods apply pneumatic fluidpressure. The preferred arrangement applies pneumatic fluid pressuresthat are both above and below atmospheric pressure and that vary betweenhigh and low relative pressure conditions.

Another aspect of the invention provides an actuator having a chamberthat conveys pneumatic pressure to the diaphragm for moving liquidthrough the pumping mechanism. According to this aspect of theinvention, an insert occupies the chamber. The insert helps dampen anddirect the pneumatic pressure upon the diaphragm, negating transientthermal effects that may arise during the conveyance of pneumaticpressure.

In a preferred embodiment, the insert made of an open cell porousmaterial.

Another aspect of the invention periodically measures fluid pressure inthe actuator chamber to derive liquid volumes moved by the pump chamber.

Other features and advantages of the inventions are set forth in thefollowing specification and attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view an automated peritoneal dialysis systemthat embodies the features of the invention, with the associateddisposable liquid delivery set ready for use with the associated cycler;

FIG. 2 is a perspective view of the cycler associated with the systemshown in FIG. 1, out of association with the disposable liquid deliveryset;

FIG. 3 is a perspective view of the disposable liquid delivery set andattached cassette that are associated with the system shown in FIG. 1

FIGS. 4 and 5 are perspective views of the organizer that is associatedwith the set shown in FIG. 3 in the process of being mounted on thecycler;

FIGS. 6 and 7 are perspective views of loading the disposable cassetteattached to the set shown in FIG. 3 into the cycler for use;

FIG. 8 is an exploded perspective view of one side of the cassetteattached to the disposable set shown in FIG. 3;

FIG. 8A is a plan view of the one side of the cassette shown in FIG. 8,showing the liquid paths within the cassette;

FIG. 8B is a plan view of the other side of the cassette shown in FIG.8, showing the pump chambers and valve stations within the cassette;

FIG. 8C is an enlarged side section view of a typical cassette valvestation shown in FIG. 8B;

FIG. 9 is perspective view of the cycle shown in FIG. 2 with its housingremoved to show its interior;

FIG. 10 is an exploded perspective view showing the main operatingmodules housed within the interior of the cycler;

FIG. 11 is an enlarged perspective view of the cassette holder modulehoused within the cycler;

FIGS. 12A and 12B are exploded views of the cassette holder module shownin FIG. 11;

FIG. 13 is a perspective view of the operative front side of the fluidpressure piston housed within the cassette module shown in FIG. 11;

FIG. 14A is a perspective view of the back side of the fluid pressurepiston shown in FIG. 13;

FIG. 14B is a perspective view of an alternative, preferred embodimentof a fluid pressure piston that can be used with the system shown inFIG. 1;

FIGS. 15A and 15B are top sectional views taken generally along line15A--15A in FIG. 11, showing the interaction between the pressure plateassembly and the fluid pressure piston within the module shown in FIG.11, with FIG. 15A showing the pressure plate holding the piston in an atrest position and FIG. 15B showing the pressure plate holding the pistonin an operative position against the cassette;

FIGS. 16A and 16B are side sectional view of the operation of theoccluder assembly housed within the module shown in FIG. 11, with FIG.16A showing the occluder assembly in a position allowing liquid flow andFIG. 16B showing the occluder assembly in a position blocking liquidflow;

FIG. 17 is a perspective view of the fluid pressure manifold modulehoused within the cycler;

FIG. 18 is an exploded perspective view of interior of the fluidpressure manifold module shown in FIG. 17;

FIG. 19 is an exploded perspective view of the manifold assembly housedwithin the module shown in FIG. 18;

FIG. 20 is a plan view of the interior of the base plate of the manifoldassembly shown in FIG. 19, showing the paired air ports and conductionpathways formed therein;

FIG. 21 is a plan view of the outside of the base plate of the manifoldassembly shown FIG. 19, also showing the paired air ports;

FIG. 22 is an exploded perspective view of the attachment of a pneumaticvalve on the outside of the base plate of the manifold assembly shown inFIG. 19, in registry over a pair of air ports;

FIG. 23 is a schematic view of the pressure supply system associatedwith the air regulation system that the manifold assembly shown in FIG.19 defines;

FIG. 24 is a schematic view of the entire air regulation system that themanifold assembly shown in FIG. 19 defines;

FIG. 25 is a flow chart showing the operation of the main menu andultrafiltration review interfaces that the controller for the cyclershown in FIG. 1 employs;

FIG. 26 is a flow chart showing the operation of the therapy selectioninterfaces that the controller for the cycler shown in FIG. 1 employs;

FIG. 27 is a flow chart showing the operation of the set up interfacesthat the controller for the cycler shown in FIG. 1 employs:

FIG. 28 is a flow chart showing the operation of the run time interfacesthat the controller for the cycler shown in FIG. 1 employs;

FIG. 29 is a flow chart showing the operation of the backgroundmonitoring that the controller for the cycler shown in FIG. 1 employs;

FIG. 30 is a flow chart showing the operation of the alarm routines thatthe controller for the cycler shown in FIG. 1 employs;

FIG. 31 is a flow chart showing the operation of the post therapyinterfaces that the controller for the cycler shown in FIG. 1 employs;

FIG. 32 is a diagrammatic representation of sequence of liquid flowthrough the cassette governed by the cycler controller during a typicalfill phase of an APD procedure;

FIG. 33 is a diagrammatic representation of sequence of liquid flowthrough the cassette governed by the cycler controller during a dwellphase (replenish heater bag) of an APD procedure;

FIG. 34 is a diagrammatic representation of sequence of liquid flowthrough the cassette governed by the cycler controller during a drainphase of an APD procedure; and

FIG. 35 is a diagrammatic representation of sequence of liquid flowthrough the cassette governed by the cycler controller during a lastdwell of an APD procedure.

The invention may be embodied in several forms without departing fromits spirit or essential characteristics. The scope of the invention isdefined in the appended claims, rather than in the specific descriptionpreceding them. All embodiments that fall within the meaning and rangeof equivalency of the claims are therefore intended to be embraced bythe claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows an automated peritoneal dialysis system 10 that embodiesthe features of the invention. The system 10 includes three principalcomponents. These are a liquid supply and delivery set 12; a cycler 14that interacts with the delivery set 12 to pump liquid through it; and acontroller 16 that governs the interaction to perform a selected APDprocedure. In the illustrated and preferred embodiment, the cycler andcontroller are located within a common housing 82.

The cycler 14 is intended to be a durable item capable of long term,maintenance free use. As FIG. 2 shows, the cycler 14 also presents acompact footprint, suited for operation upon a table top or otherrelatively small surface normally found in the home. The cycler 14 isalso lightweight and portable.

The set 12 is intended to be a single use, disposable item. The userloads the set 12 on the cycler 14 before beginning each APD therapysession. The user removes the set 12 from the cycler 14 upon thecompleting the therapy session and discards it.

In use (as FIG. 1 shows), the user connects the set 12 to his/herindwelling peritoneal catheter 18. The user also connects the set 12 toindividual bags 20 containing sterile peritoneal dialysis solution forinfusion. The set 12 also connects to a bag 22 in which the dialysissolution is heated to a desired temperature (typically to about 37degrees C.) before infusion.

The controller 16 paces the cycler 14 through a prescribed series offill, dwell, drain cycles typical of an APD procedure.

During the fill phase, the cycler 14 infuses the heated dialysatethrough the set 12 and into the patient's peritoneal cavity. Followingthe dwell phase, the cycler 14 institutes a drain phase, during whichthe cycler 14 discharges spent dialysis solution from the patient'speritoneal cavity through the set into a nearby drain (not shown).

As FIG. 1 shows, the cycler 14 does not require hangers for suspendingthe source solution bags 20 at a prescribed head height above it. Thisis because the cycler 14 is not a gravity flow system. Instead, usingquiet, reliable pneumatic pumping action, the cycler 14 emulates gravityflow, even when the source solution bags 20 lie right alongside it, orin any other mutual orientation.

The cycler 14 can emulate a fixed head height during a given procedure.Alternatively, the cycler 14 can change the head height to eitherincrease or decrease the rate of flow during a procedure. The cycler 14can emulate one or more selected head height differentials regardless ofthe actual head height differential existing between the patient'speritoneal cavity and the external liquid sources or destinations.

Because the cycler 14 establishes essentially an artificial head height,it has the flexibility to interact with and adapt quickly to theparticular physiology and relative elevation of the patient.

The compact nature and silent, reliable operating characteristics of thecycler 14 make it ideally suited for bedside use at home while thepatient is asleep.

The principal system components will now be individually discussed ingreater detail.

I. THE DISPOSABLE SET

As FIG. 3 best shows, the set 12 includes a cassette 24 to which lengthsof flexible plastic tubes 26/28/30/32/34 are attached.

FIG. 3 shows the disposable liquid supply and delivery set 12 before itis readied for use in association with the cycler 14. FIG. 1 shows thedisposable set 12 when readied for use in association with the cycler14.

In use (as FIG. 1 shows), the distal ends of the tubes 26 to 34 connectoutside the cycler 14 to the bags 20 of fresh peritoneal dialysissolution, to the liquid heater bag 22, to the patient's indwellingcatheter 18, and to a drain (not shown).

For this reason, the tube 34 carries a conventional connector 36 forattachment to the patient's indwelling catheter 18. Other tubes 26/30/32carry conventional connectors 38 for attachment to bag ports. Tube 32contains a Y-connector 31, creating tubing branches 32A and 32B, each ofwhich may connect to a bag 20.

The set 12 may contain multiple branches to accommodate attachment tomultiple bags 20 of dialysis solution.

The tube 28 has a drain connector 39. It serves to discharge liquid intothe external drain (not shown).

The tubing attached to the set carries an inline, manual clamp 40,except the drain tube 28.

As FIGS. 1 and 3 show, the set 12 also preferably includes a branchconnector 54 on the drain tube 28. The branch connector 54 creates atubing branch 28A that carries a connector 55. The connector 55 attachesto a mating connector on an effluent inspection bag (not shown).

Once attached, the patient can divert a volume (about 25 ml) of spentdialysate through branch 28A into the inspection bag during the firstdrain cycle. The bag allows the patient to inspect for cloudy effluent,which is an indication of peritonitis.

As FIGS. 6 and 7 show, in use, the cassette 24 mounts inside a holder100 in the cycler 14 (see FIG. 1, too). The details of the holder 100will be discussed in greater detail later. The holder 100 orients thecassette 24 for use vertically, as FIG. 7 shows.

As FIGS. 3 to 5 show, the set 12 preferably includes an organizer 42that holds the distal tube ends in a neat, compact array. Thissimplifies handling and shortens the set up time.

The organizer 42 includes a body with a series of slotted holders 44.The slotted holders 44 receive the distal tube ends with a friction fit.

The organizer 42 includes slot 46 that mates with a tab 48 carried onoutside of the cassette holder 100. A pin 50 on the outside of thecassette holder 100 also mates with an opening 52 on the organizer 42.These attach the organizer 42 and attached tube ends to the outside ofthe cassette holder 100 (as FIGS. 1 and 5 show).

Once attached, the organizer 42 frees the user's hands for making therequired connections with the other elements of the cycler 14. Havingmade the required connections, the user can remove and discard theorganizer 42.

The cassette 24 serves in association with the cycler 14 and thecontroller 16 to direct liquid flow among the multiple liquid sourcesand destinations that a typical APD procedure requires. As will bedescribed in greater detail later, the cassette 24 provides centralizedvalving and pumping functions in carrying out the selected APD therapy.

FIGS. 8/8A/8B show the details of the cassette 24. As FIG. 8 shows, thecassette 24 includes an injection molded body having front and backsides 58 and 60. For the purposes of description, the front side 58 isthe side of the cassette 24 that, when the cassette 24 is mounted in theholder 100, faces away from the user.

A flexible diaphragm 59 and 61 overlies the front side and back sides 58and 60 of the cassette 24, respectively.

The cassette 24 is preferably made of a rigid medical grade plasticmaterial. The diaphragms 59/61 are preferably made of flexible sheets ofmedical grade plastic. The diaphragms 59/61 are sealed about theirperipheries to the peripheral edges of the front and back sides 58/60 ofthe cassette 24.

The cassette 24 forms an array of interior cavities in the shapes ofwells and channels. The interior cavities create multiple pump chambersP1 and P2 (visible from the front side 58 of the cassette 24, as FIG. 8Bshows). The interior cavities also create multiple paths F1 to F9 toconvey liquid (visible from the back side 60 of the cassette 24, asFIGS. 8 and 8A shows). The interior cavities also create multiple valvestations V1 to V10 (visible from the front side 58 of the cassette 24,as FIG. 8B shows). The valve stations V1 to V10 interconnect themultiple liquid paths F1 to F9 with the pump chambers P1 and P2 and witheach other.

The number and arrangement of the pump chambers, liquid paths, and valvestations can vary.

A typical APD therapy session usually requires five liquidsources/destinations. The cassette 24 that embodies the features of theinvention provides these connections with five exterior liquid lines(i.e., the flexible tubes 26 to 32), two pump chambers P1 and P2, nineinterior liquid paths F1 to F9, and ten valve stations V1 to V10.

The two pump chambers P1 and P2 are formed as wells that open on thefront side 58 of the cassette 24. Upstanding edges 62 peripherallysurround the open wells of the pump chambers P1 and P2 on the front side58 of the cassette 24 (see FIG. 8B).

The wells forming the pump chambers P1 and P2 are closed on the backside 60 of the cassette 24 (see FIG. 8), except that each pump chamberP1 and P2 includes a vertically spaced pair of through holes or ports64/66 that extend through to the back side 60 of the cassette 24.

As FIGS. 8/8A/8B show, vertically spaced ports 64(1) and 66(1) areassociated with pump chamber P1. Port 64(1) communicates with liquidpath F6, while port 66(1) communicates with liquid path F8.

As FIGS. 8/8A/8B also show, vertically spaced ports 64(2) and 66(2) areassociated with pump chamber P2. Port 64(2) communicates with liquidpath F7, while port 66(2) communicates with liquid path F9.

As will become apparent, either port 64(1)/(2) or 66(1)/(2) can serveits associated chamber P1/P2 as an inlet or an outlet. Alternatively,liquid can be brought into and discharged out of the chamber P1/P2through the same port associated 64(1)/(2) or 66(1)/(2).

In the illustrated and preferred embodiment, the ports 64/66 are spacedso that, when the cassette 24 is oriented vertically for use, one port64(1)/(2) is located higher than the other port 66(1)/(2) associatedwith that pump chamber P1/P2. As will be described in greater detaillater, this orientation provides an important air removal function.

The ten valve stations V1 to V10 are likewise formed as wells open onthe front side 58 of the cassette 24. FIG. 8C shows a typical valvestation V_(N). As FIG. 8C best shows, upstanding edges 62 peripherallysurround the open wells of the valve stations V1 to V10 on the frontside 58 of the cassette 24.

As FIG. 8C best shows, the valve stations V1 to V10 are closed on theback side 60 of the cassette 24, except that each valve station V_(N)includes a pair of through holes or ports 68 and 68'. One port 68communicates with a selected liquid path F_(N) on the back side 60 ofthe cassette 24. The other port 68' communicates with another selectedliquid path F_(N), on the back side 60 of the cassette 24.

In each valve station V_(N), a raised valve seat 72 surrounds one of theports 68. As FIG. 8C best shows, the valve seat 72 terminates lower thanthe surrounding peripheral edges 62. The other port 68' is flush withthe front side 58 of the cassette.

As FIG. 8C continues to show best, the flexible diaphragm 59 overlyingthe front side 58 of the cassette 24 rests against the upstandingperipheral edges 62 surrounding the pump chambers and valve stations.With the application of positive force uniformly against this side 58 ofthe cassette 24 (as shown by the f-arrows in FIG. 8C), the flexiblediaphragm 59 seats against the upstanding edges 62. The positive forceforms peripheral seals about the pump chambers P1 and P2 and valvestations V1 to V10. This, in turn, isolates the pump chambers P1 and P2and valve stations V1 to V10 from each other and the rest of the system.The cycler 14 applies positive force to the front cassette side 58 forthis very purpose.

Further localized application of positive and negative fluid pressuresupon the regions of the diaphragm 59 overlying these peripherally sealedareas serve to flex the diaphragm regions within these peripherallysealed areas.

These localized applications of positive and negative fluid pressures onthe diaphragm regions overlying the pump chambers P1 and P2 serve tomove liquid out of and into the chambers P1 and P2.

Likewise, these localized applications of positive and negative fluidpressure on the diaphragm regions overlying the valve stations V1 to V10will serve to seat and unseat these diaphragm regions against the valveseats 72, thereby closing and opening the associated valve port 68. FIG.8C shows in solid and phantom lines the flexing of the diaphragm 59relative to a valve seat 72.

In operation, the cycler 14 applies localized positive and negativefluid pressures to the diaphragm 59 for opening and closing the valveports.

The liquid paths F1 to F9 are formed as elongated channels that are openon the back side 60 of the cassette 24. Upstanding edges 62 peripherallysurround the open channels on the back side 60 of the cassette 24.

The liquid paths F1 to F9 are closed on the front side 58 of thecassette 24, except where the channels cross over valve station ports68/68' or pump chamber ports 64(1)/(2) and 66(1)/(2).

The flexible diaphragm 61 overlying the back side 60 of the cassette 24rests against the upstanding peripheral edges 62 surrounding the liquidpaths F1 to F9. With the application of positive force uniformly againstthis side 60 of the cassette 24, the flexible diaphragm 61 seats againstthe upstanding edges 62. This forms peripheral seals along the liquidpaths F1 to F9. In operation, the cycler 14 also applies positive forceto the diaphragm 61 for this very purpose.

As FIGS. 8/8A/8B show, five premolded tube connectors 27/29/31/33/35extend out along one side edge of the cassette 24. When the cassette 24is vertically oriented for use, the tube connectors 27 to 35 arevertically stacked one above the other. The first tube connector 27 isthe uppermost connector, and the fifth tube connector 35 is thelowermost connector.

This ordered orientation of the tube connectors 27 to 35 provides acentralized, compact unit. It also makes it possible to cluster thevalve stations within the cassette 24 near the tube connectors 27 to 35.

The first through fifth tube connectors 27 to 35 communicate withinterior liquid paths F1 to F5, respectively. These liquid paths F1 toF5 constitute the primary liquid paths of the cassette 24, through whichliquid enters or exits the cassette 24.

The remaining interior liquid paths F6 to F9 of the cassette 24constitute branch paths that link the primary liquid paths F1 to F5 tothe pump chambers P1 and P2 through the valve stations V1 to V10.

Because the pump chambers P1 and P2 are vertically oriented during use,air entering the pump chambers P1/P2 during liquid pumping operationswill accumulate near the upper port 64 in each pump chamber P1/P2.

The liquid paths F1 to F9 and the valve stations V1 to V10 arepurposefully arranged to isolate the patient's peritoneal cavity fromthe air that the pump chambers P1/P2 collect. They are also purposefullyarranged so that this collected air can be transferred out of the pumpchambers P1/P2 during use.

More particularly, the cassette 24 isolates selected interior liquidpaths from the upper ports 64 of the pump chambers P1 and P2. Thecassette 24 thereby isolates these selected liquid paths from the airthat accumulates in the pump chambers P1/P2. These air-isolated liquidpaths can be used convey liquid directly into and from the patient'speritoneal cavity.

The cassette 24 also connects other selected liquid paths only to theupper ports 64(1)/(2) of the pump chambers P1 and P2. These liquid pathscan be used to transfer air out of the respective pump chamber P1/P2.These liquid paths can also be used to convey liquid away from thepatient to other connected elements in the system 10, like the heaterbag 22 or the drain.

In this way, the cassette 24 serves to discharge entrapped air throughestablished noncritical liquid paths, while isolating the criticalliquid paths from the air. The cassette 24 thereby keeps air fromentering the patient's peritoneal cavity.

More particularly, valve stations V1 to V4 serve only the upper ports64(1)/(2) of both pump chambers P1 and P2. These valve stations V1 to inturn, serve only the primary liquid paths F1 and F2. Branch liquid pathF6 links primary paths F1 and F2 with the upper port 64(1) of pumpchamber P1 through valve stations V1 and V2. Branch liquid path F7 linksprimary paths F1 and F2 with the upper port 64(2) of pump chamber P2through valve stations V3 and V4.

These primary paths F1 and F2 can thereby serve as noncritical liquidpaths, but not as critical liquid paths, since they are not isolatedfrom air entrapped within the pumping chambers P1/P2. By the same token,the primary paths F1 and F2 can serve to convey entrapped air from thepump chambers P1 and P2.

Tubes that, in use, do not directly convey liquid to the patient can beconnected to the noncritical liquid paths F1 and F2 through the uppertwo connectors 27 and 29. One tube 26 conveys liquid to and from theheater bag 22. The other tube 28 conveys spent peritoneal solution tothe drain.

When conveying liquid to the heater bag 22 or to the drain, these tubes26/28 can also carry air that accumulates in the upper region of thepump chambers P1/P2. In this arrangement, the heater bag 22, like thedrain, serves as an air sink for the system 10.

Valve stations V5 to V10 serve only the lower ports 66(1)/(2) of bothpump chambers P1 and P2. These valve stations V5 to V10, in turn, serveonly the primary liquid paths F3; F4; and F5. Branch liquid path F8links primary paths F3 to F5 with the lower port 66(1) of pump chamberP1 through valve stations V8; V9; and V10. Branch liquid path F9 linksprimary paths F3 to F5 with the lower port 66(2) of pump chamber P2through valve stations V5; V6; and V7.

Because the primary paths F3 to F5 are isolated from communication withthe upper ports 64 of both pump chambers P1 and P2, they can serve ascritical liquid paths.

Thus, the tube 34 that conveys liquid directly to the patient'sindwelling catheter can be connected to one of the lower threeconnectors 31/33/35 (i.e., to the primary liquid paths F3 to F5).

The same tube 34 also carries spent dialysate from the patient'speritoneal cavity. Likewise, the tubes 30/32 that carry sterile sourceliquid into the pump chambers enter through the lower pump chamber ports66(1)/(2).

This arrangement makes it unnecessary to incorporate bubble traps andair vents in the tubing serving the cassette. The cassette is its ownself contained air trap.

II. THE CYCLER

As FIGS. 9 and 10 best show, the cycler 14 carries the operatingelements essential for an APD procedure within a portable housing 82that occupies a relatively small footprint area (as FIGS. 1 and 2 alsoshow).

As already stated, the housing 82 encloses the cycle controller 16.

The housing 82 also encloses a bag heater module 74 (see FIG. 9). Itfurther encloses a pneumatic actuator module 76. The pneumatic actuatormodule 76 also incorporates the cassette holder 100 already described,as well as a failsafe liquid shutoff assembly 80, which will bedescribed later.

The housing 82 also encloses a source 84 of pneumatic pressure and anassociated pneumatic pressure distribution module 88, which links thepressure source 84 with the actuator module 76.

The housing 82 also encloses an AC power supply module 90 and a back-upDC battery power supply module 92 for the cycler 14.

Further structural and functional details of these operating modules ofthe cycler 14 will be described next.

(A) The Bag Heating Module

The bag heating module 74 includes an exterior support plate 94 on thetop of the cycler housing 82 for carrying the heater bag 22 (as FIG. 1shows). The support plate 94 is made of a heat conducting material, likealuminum.

As FIG. 9 shows, the module 74 includes a conventional electricalresistance heating strip 96 that underlies and heats the support plate94.

Four thermocouples T1/T2/T3/T4 monitor the temperatures at spacedlocations on the left, right, rear, and center of the heating strip 96.Fifth and sixth thermocouples T5/T6 (see FIGS. 2 and 10) independentlymonitor the temperature of the heater bag 22 itself.

A circuit board 98 (see FIG. 9) receives the output of the thermocouplesT1 to T6. The board 98 conditions the output before transmitting it tothe controller 16 for processing.

In the preferred embodiment, the controller 16 includes a heater controlalgorithm that elevates the temperature of liquid in the heater bag 22to about 33 degrees C. before the first fill cycle. A range of othersafe temperature settings could be used, which could be selected by theuser. The heating continues as the first fill cycle proceeds until theheater bag temperature reaches 36 degrees C.

The heater control algorithm then maintains the bag temperature at about36 degrees C. The algorithm functions to toggle the heating strip 96 onand off at a sensed plate temperature of 44 degrees C. to assure thatplate temperature never exceeds 60 degrees C.

(B) The Pneumatic Actuator Module

The cassette holder 100, which forms a part of the pneumatic actuatormodule 76, includes a front plate 105 joined to a back plate 108 (seeFIG. 12A). The plates 105/108 collectively form an interior recess 110.

A door 106 is hinged to the front plate 105 (see FIGS. 6 and 7). Thedoor 106 moves between an opened position (shown in FIGS. 6 and 7) and aclosed position (shown in FIGS. 1; 2; and 11).

A door latch 115 operated by a latch handle 111 contacts a latch pin 114when the door 106 is closed. Moving the latch handle 111 downward whenthe door 106 is closed engages the latch 115 to the pin 114 to lock thedoor 106 (as FIGS. 4 and 5 show). Moving the latch handle 111 upwardwhen the door 106 is closed releases the latch 115 from the pin 114.This allows the door 106 to be opened (as FIG. 6 shows) to gain accessto the holder interior.

With the door 106 opened, the user can insert the cassette 24 into therecess 110 with its front side 58 facing the interior of the cycler 14(as FIGS. 6 and 7 show).

The inside of the door 106 carries an upraised elastomeric gasket 112positioned in opposition to the recess 110. Closing the door 106 bringsthe gasket 112 into facing contact with the diaphragm 61 on the backside 60 of the cassette 24.

The pneumatic actuator module 76 contains a pneumatic piston headassembly 78 located behind the back plate 108 (see FIG. 12A).

The piston head assembly 78 includes a piston element 102. As FIGS. 12A;13 and 14 show, the piston element 102 comprises a molded or machinedplastic or metal body. The body contains two pump actuators PA1 and PA2and ten valve actuators VA1 to VA10. The pump actuators PA1/PA2 and thevalve actuators VA1 to VA10 are mutually oriented to form a mirror imageof the pump stations P1/P2 and valve stations V1 to V10 on the frontside 58 of the cassette 24.

Each actuator PA1/PA2/VA1 to VA10 includes a port 120. The ports 120convey positive or negative pneumatic pressures from the pneumaticpressure distribution module 88 (as will be described in greater detaillater).

As FIG. 13 best shows, interior grooves 122 formed in the piston element102 surround the pump and valve actuators PA1/PA2/VA1 to VA10. Apreformed gasket 118 (see FIG. 12A) fits into these grooves 122. Thegasket 118 seals the peripheries of the actuators PA1/PA2/VA1 to VA10against pneumatic pressure leaks.

The configuration of the preformed gasket 118 follows the pattern ofupstanding edges that peripherally surround and separate the pumpchambers P1 and P2 and valve stations V1 to V10 on the front side 58 ofthe cassette 24.

The piston element 102 is attached to a pressure plate 104 within themodule 76 (see FIG. 12B). The pressure plate 104 is, in turn, supportedon a frame 126 for movement within the module 76.

The side of the plate 104 that carries the piston element 102 abutsagainst a resilient spring element 132 in the module 76. In theillustrated and preferred embodiment, the spring element 132 is made ofan open pore foam material.

The frame 126 also supports an inflatable main bladder 128. Theinflatable bladder 128 contacts the other side of the plate 104.

The piston element 102 extends through a window 134 in the springelement 132 (see FIG. 12A). The window 134 registers with the cassettereceiving recess 110.

With a cassette 24 fitted into the recess 110 and the holder door 106closed, the piston element 102 in the window 134 is mutually alignedwith the diaphragm 59 of the cassette 24 in the holder recess 110.

As FIG. 15A shows, when the main bladder 128 is relaxed (i.e., notinflated), the spring element 132 contacts the plate 104 to hold thepiston element 102 away from pressure contact with a cassette 24 withinthe holder recess 110.

As will be described in greater detail later, the pneumatic pressuredistribution module 88 can supply positive pneumatic pressure to themain bladder 128. This inflates the bladder 128.

As FIG. 15B shows, when the main bladder 128 inflates, it presses theplate 104 against the spring element 132. The open cell structure of thespring element 132 resiliently deforms under the pressure. The pistonelement 102 moves within the window 134 into pressure contact againstthe cassette diaphragm 59.

The bladder pressure presses the piston element gasket 118 tightlyagainst the cassette diaphragm 59. The bladder pressure also presses theback side diaphragm 61 tightly against the interior of the door gasket112.

As a result, the diaphragms 59 and 61 seat against the upstandingperipheral edges 62 that surround the cassette pump chambers P1/P2 andvalve stations V1 to V10. The pressure applied to the plate 104 by thebladder 128 seals the peripheries of these regions of the cassette 24.

The piston element 102 remains in this operating position as long as themain bladder 128 retains positive pressure and the door 106 remainsclosed.

In this position, the two pump actuators PA1 and PA2 in the pistonelement 102 register with the two pump chambers P1 and P2 in thecassette 24. The ten valve actuators VA1 to VA10 in the piston element102 likewise register with the ten valve stations V1 to V10 in thecassette 24.

As will be described in greater detail later, the pneumatic pressuredistribution module 88 conveys positive and negative pneumatic fluidpressure to the actuators PA1/PA2/VA1 to VA10 in a sequence governed bythe controller 16. These positive and negative pressure pulses flex thediaphragm 59 to operate the pump chambers P1/P2 and valve stations V1 toV10 in the cassette 24. This, in turn, moves liquid through the cassette24.

Venting the positive pressure in the bladder 128 relieves the pressurethe plate 104 applies to the cassette 24. The resilient spring element132 urges the plate 104 and attached piston element 102 away frompressure contact with the cassette diaphragm 59. In this position, thedoor 106 can be opened to unload the cassette 24 after use.

As FIG. 12A shows, the gasket 118 preferably includes an integralelastomeric membrane 124 stretched across it. This membrane 124 isexposed in the window 134. It serves as the interface between the pistonelement 102 and the diaphragm 59 of the cassette 24, when fitted intothe holder recess 110.

The membrane 124 includes one or more small through holes 125 in eachregion overlying the pump and valve actuators PA1/PA2/VA1 to VA10. Theholes 125 are sized to convey pneumatic fluid pressure from the pistonelement actuators to the cassette diaphragm 59. Nevertheless, the holes125 are small enough to retard the passage of liquid. This forms aflexible splash guard across the exposed face of the gasket 118.

The splash guard membrane 124 keeps liquid out of the pump and valveactuators PA1/PA2/VA1 to VA10, should the cassette diaphragm 59 leak.The splash guard membrane 124 also serves as a filter to keepparticulate matter out of the pump and valve actuators of the pistonelement 102. The splash guard membrane 124 can be periodically wipedclean when cassettes are exchanged.

As FIG. 12A shows, inserts 117 preferably occupy the pump actuators PA1and PA2 behind the membrane 124.

In the illustrated and preferred embodiment, the inserts 117 are made ofan open cell foam material. The inserts 117 help dampen and direct thepneumatic pressure upon the membrane 124. The presence of inserts 117stabilizes air pressure more quickly within the pump actuators PA1 andPA2, helping to negate transient thermal effects that arise during theconveyance of pneumatic pressure.

(C) The Liquid Shutoff Assembly

The liquid shutoff assembly 80, which forms a part of the pneumaticactuator module 76, serves to block all liquid flow through the cassette24 in the event of a power failure or another designated errorcondition.

As FIG. 12B shows, the liquid shutoff assembly 80 includes a movableoccluder body 138 located behind the pressure plate frame 126. Theoccluder body 138 has a side hook element 140 that fits into a slot 142in the pressure plate frame 126 (see FIGS. 16A/B). This hook-in-slot fitestablishes a contact point about which the occluder body 138 pivots onthe pressure plate frame 126.

The occluder body 138 includes an elongated occluder blade 144 (seeFIGS. 12A; 15; and 16). The occluder blade 144 extends through a slot146 in the front and back plates 105/108 of the holder 100. When theholder door 106 is closed, the blade 144 faces an elongated occluder bar148 carried on the holder door 106 (see FIGS. 15 and 16).

When the cassette 24 occupies the holder recess 110 (see FIG. 7) and theholder door 106 is closed, all tubing 26 to 34 attached to the cassette24 passes between the occluder blade 144 and the occluder bar 148 (asFIGS. 15 and 16 show).

In the illustrated and preferred embodiment, a region 145 of theflexible tubing 26 to 34 is held in a mutually close relationship nearthe cassette 24 (see FIG. 3). This bundled tubing region 145 furthersimplifies the handling of the cassette 24. This bundled region 145 alsoarranges the cassette tubing 26 to 34 in a close, side by siderelationship in the region between the occluder blade 144 and bar 148(see FIG. 7).

In the illustrated and preferred embodiment, the sidewalls of theflexible tubing 26 to 34 are RF surface welded together to form thebundled region 145.

Pivotal movement of the occluder body 138 moves the occluder blade 144toward or away from the occluder bar 148. When spaced apart (as FIG. 16Ashows), the occluder blade and bar 144/148 allow clear passage of thecassette tubing 26 to 34. When brought together (as FIG. 16B shows), theoccluder blade and bar 144/148 crimp the cassette tubing 26 to 34closed. Occluder springs 150 carried within sleeves 151 normally biasthe occluder blade and bar 144/148 together.

An occluder bladder 152 occupies the space between the occluder body 138and the frame 126 (see FIG. 12B).

As FIG. 16B shows, when the occluder bladder 152 is relaxed (i.e., notinflated), it makes no contact against the occluder body 138. Theoccluder springs 150 urge the occluder blade and bar 144/148 together,simultaneously crimping all cassette tubing 26 to 34 closed. Thisprevents all liquid flow to and from the cassette 24.

As will be described in greater detail later, the pneumatic pressuredistribution module 88 can supply positive pneumatic pressure to theoccluder bladder 152. This inflates the bladder 128.

As FIG. 16A shows, when the occluder bladder 152 inflates, it pressesagainst the occluder body 138 to pivot it upward. This moves theoccluder blade 144 away from the occluder bar 158. This permits liquidto flow through all tubing to and from the cassette 24.

The occluder blade and bar 144/148 remain spaced apart as long as theoccluder bladder 152 retains positive pressure.

Venting of positive pressure relaxes the occluder bladder 152. Theoccluder springs 150 immediately urge the occluder blade and bar 144/148back together to crimp the tubing closed.

As will be described in greater detail later, an electrically actuatedvalve C6 communicates with the occluder bladder 152. When receivingelectrical power, the valve C6 is normally closed. In the event of apower loss, the valve C6 opens to vent the occluder bladder 152,crimping the cassette tubing 26 to 34 closed.

The assembly 80 provides a pneumatically actuated fail-safe liquid shutoff for the pneumatic pumping system.

(D) The Pneumatic Pressure Source

The pneumatic pressure source 84 comprises a linear vacuum pump and aircompressor capable of generating both negative and positive airpressure. In the illustrated and preferred embodiment, the pump 84 is aconventional air compressor/vacuum pump commercially available from MedoCorporation.

As FIG. 23 shows, the pump 84 includes an inlet 154 for drawing air intothe pump 84. The pump inlet 154 supplies the negative pressure requiredto operate the cycler 14.

As FIG. 23 also shows, the pump 84 also includes an outlet 156 fordischarging air from the pump 84. The pump outlet 156 supplies positivepressure required to operate the cycler 14.

FIGS. 9 and 10 also show the inlet 154 and outlet 156.

The pump inlet 154 and the pump outlet 156 communicate with ambient airvia a common vent 158 (shown schematically in FIG. 23). The vent 158includes a filter 160 that removes particulates from the air drawn intothe pump 84.

(E) The Pressure Distribution System

FIGS. 17 to 22 show the details of the pneumatic pressure distributionmodule 88. The module 88 encloses a manifold assembly 162. The manifoldassembly 162 controls the distribution of positive and negativepressures from the pump 84 to the piston element 102, the main bladder128, and the occluder bladder 152. The controller 16 provides thecommand signals that govern the operation of the manifold assembly 162.

As FIGS. 18 shows, a foam material 164 preferably lines the interior ofthe module 88 enclosing the manifold assembly 162. The foam material 164provides a barrier to dampen sound to assures quiet operation.

As FIGS. 18 and 19 show, the manifold assembly 162 includes a top plate166 and a bottom plate 168. A sealing gasket 170 is sandwiched betweenthe plates 166/168.

The bottom plate 168 (see FIGS. 20 and 21) includes an array of pairedair ports 172. FIG. 20 shows the inside surface of the bottom plate 168that faces the gasket 170 (which is designated IN in FIGS. 19 and 20).FIG. 21 shows the outside surface of the bottom plate 168 (which isdesignated OUT in FIGS. 19 and 21).

The inside surface (IN) of the bottom plate 168 also contains an arrayof interior grooves that form air conduction channels 174 (see FIG. 20).The array of paired air ports 172 communicates with the channels 174 atspaced intervals. A block 176 fastened to the outside surface (OUT) ofthe bottom plate 168 contains an additional air conduction channels 174that communicate with the channels 174 on the inside plate surface (IN)(see FIGS. 19 and 22).

Transducers 178 mounted on the exterior of the module 88 sense throughassociated sensing tubes 180 (see FIG. 18) pneumatic pressure conditionspresent at various points along the air conduction channels 174. Thetransducers 178 are conventional semiconductor piezo-resistance pressuresensors. The top of the module 88 includes stand-off pins 182 that carrya board 184 to which the pressure transducers 178 are attached.

The outside surface (OUT) of the bottom plate 168 (see FIGS. 19 and 22)carries a solenoid actuated pneumatic valves 190 connected incommunication with each pair of air ports 172. In the illustratedembodiment, there are two rows of valves 190 arranged along oppositesides of the outside surface (OUT) of the plate 168. Twelve valves 190form one row, and thirteen valves 190 form the other row.

As FIG. 22 shows, each pneumatic valve 190 is attached in communicationwith a pair of air ports 172 by screws fastened to the outside surface(OUT) of the bottom plate 168. As FIGS. 19 and 22 also show, each valve190 is electrically connected by ribbon cables 192 to the cyclercontroller 16 by contacts on a junction board 194. There are twojunction boards 194, one for each row of valves 190.

Each pneumatic valve 190 operates to control air flow through itsassociated pair of ports 172 to link the ports 172 to the various airchannels 174 the bottom plate 168 carries. As will be described ingreater detail later, some of the valves 190 are conventional three wayvalves. Others are conventional normally closed two way valves.

The air channels 174 within the manifold assembly 162 are coupled byflexible tubing 196 (see FIG. 17) to the system components that operateusing pneumatic pressure. Slots 198 in the side of the module 88accommodate the passage of the tubing 196 connected to the manifoldassembly 162.

FIGS. 9 and 10 also show the flexible tubing 196 that links the manifoldassembly 162 to the pneumatically actuated and controlled systemcomponents.

FIG. 11 further shows the tubing 196 from the manifold assembly 162entering the pneumatic actuator module 76, where they connect to themain bladder 128, the occluder bladder 152, and the piston element 102.FIG. 14A further shows the T-fittings that connect the tubing 196 to theports of the valve actuators VA1 to VA10 and the ports of the pumpactuators PA1/PA2 of the piston element 102. These connections are madeon the back side of the piston element 102.

1. The Pressure Regulation System

The air conduction passages 174 and the flexible tubing 196 associatedwith the manifold assembly 162 define a fluid pressure regulation system200 that operates in response to command signals from the cyclercontroller 16. FIGS. 23 and 24 show the details of the air regulationsystem 200 in schematic form.

In response to the command signals of the controller 16, the pressureregulation system 200 directs the flow of positive and negativepneumatic pressures to operate the cycler 14. When power is applied, thesystem 200 maintains the occluder assembly 80 in an open,flow-permitting condition; it seals the cassette 24 within the holder100 for operation; and it conveys pneumatic pressure to the pistonelement 102 to move liquid through the cassette 24 to conduct an APDprocedure. The pressure regulation system 200 also provides informationthat the controller 16 processes to measure the volume of liquidconveyed by the cassette 24.

a. Pressure Supply Network

As FIG. 23 shows, the regulation system 200 includes a pressure supplynetwork 202 having a positive pressure side 204 and a negative pressureside 206. The positive and negative pressure sides 204 and 206 can eachbe selectively operated in either a low-relative pressure mode orhigh-relative pressure mode.

The controller 16 calls for a low-relative pressure mode when the cycler14 circulates liquid directly through the patient's indwelling catheter18 (i.e., during patient infusion and drain phases). The controller 16calls for a high-relative pressure mode when the cycler 14 circulatesliquid outside the patient's indwelling catheter 18 (i.e., duringtransfers of liquid from supply bags 20 to the heater bag 22).

In other words, the controller 16 activates the low-relative pressuremode when considerations of patient comfort and safety predominate.

The controller 16 activates the high-relative pressure mode whenconsiderations of processing speed predominate.

In either mode, the pump 84 draws air under negative pressure from thevent 158 through an inlet line 208. The pump 84 expels air underpositive pressure through an outlet line 210 to the vent 158.

The negative pressure supply side 206 communicates with the pump inletline 208 through a negative pressure branch line 212. The three waypneumatic valve DO carried on the manifold assembly 162 controls thiscommunication.

The branch line 212 supplies negative pressure to a reservoir 214carried within the cycler housing 82 (this can be seen in FIGS. 9 and10). The reservoir 214 preferably has a capacity greater than about 325cc and a collapse pressure of greater than about -10 psig. Thetransducer XNEG carried on the manifold assembly 162 senses the amountof negative pressure stored within the negative pressure reservoir 214.

When in the high-relative negative pressure mode, the transducer XNEGtransmits a control signal when the predefined high-relative negativepressure of -5.0 psig is sensed. When in the low-relative negativepressure mode, the transducer XNEG transmits a control signal when thepredefined low-relative negative pressure of -1.2 psig is sensed. Thepressure reservoir 214 serves as both a low-relative and a high-relativepressure reservoir, depending upon the operating mode of the cycler 14.

The positive pressure supply side 204 communicates with the pump outletline 210 through a main positive pressure branch line 216. The three waypneumatic valve C5 controls this communication.

The main branch line 216 supplies positive pressure to the main bladder128, which seats the piston head 116 against the cassette 24 within theholder 100. The main bladder 128 also serves the system 202 as apositive high pressure reservoir.

The main bladder 128 preferably has a capacity of greater than about 600cc and a fixtured burst pressure over about 15 psig.

Transducer XHPOS carried on the manifold assembly 162 senses the amountof positive pressure within the main bladder 128. Transducer XHPOStransmits a control signal when the predetermined high-relative pressureof 7.5 psig is sensed.

A first auxiliary branch line 218 leads from the main branch line 216 toa second positive pressure reservoir 220 carried within the housing(which can also be seen in FIGS. 9 and 10). The two way, normally closedpneumatic valve A6 carried by the manifold assembly 168 controls thepassage positive pressure to the second reservoir 220. The secondreservoir 220 serves the system 202 as a reservoir for low-relativepositive pressure.

The second reservoir 220 preferably has a capacity of greater than about325 cc and a fixtured burst pressure greater than about 10 psig.

Transducer XLPOS carried on the manifold assembly 162 senses the amountof positive pressure within the second pressure reservoir 220.Transducer XLPOS is set to transmit a control signal when thepredetermined low-relative pressure of 2.0 psig is sensed.

The valve A6 divides the positive pressure supply side 204 into ahigh-relative positive pressure region 222 (between valve station C5 andvalve station A6) and a low-relative positive pressure region 224(between valve station A6 and the second reservoir 220).

A second auxiliary positive pressure branch line 226 leads from the mainbranch line 216 to the occluder bladder 152 through three way pneumaticvalve C6. The occluder bladder 152 also serves the system 202 as apositive high pressure reservoir.

A bypass branch line 228 leads from the main branch 216 to the vent 158through the two way, normally closed valve A5. The valve C6 alsocommunicates with the bypass branch line 228.

The pressure supply network 202 has three modes of operation. In thefirst mode, the network 202 supplies the negative pressure side 206. Inthe second mode, the network 202 supplies the positive pressure side204. In the third mode, the network 202 supplies neither negative orpositive pressure side 204/206, but serves to circulate air in acontinuous manner through the vent 158.

With the three modes of operation, the pump 84 can be continuouslyoperated, if desired. This avoids any time delays and noise occasionedby cycling the pump 84 on and off.

In the first mode, valve station D0 opens communication between thenegative branch line 212 and the pump inlet line 208. Valve C5 openscommunication between the pump outline line 210 and the vent 158, whileblocking communication with the main positive branch line 216.

The pump 84 operates to circulate air from the vent 158 through itsinlet and outlet lines 208/210 to the vent 158. This circulation alsodraws air to generating negative pressure in the negative branch line212. The reservoir 214 stores this negative pressure.

When the transducer XNEG senses its predetermined high-relative orlow-relative negative pressure, it supplies a command signal to operatevalve D0, closing communication between the pump inlet line 208 and thenegative branch line 212.

In the second mode, valve D0 closes communication between the negativebranch line 212 and the pump inlet line 208. Valve C5 closescommunication with the vent 158, while opening communication with themain positive branch line 216.

The pump 84 operates to convey air under positive pressure into the mainpositive branch line 216. This positive pressure accumulates in the mainbladder 128 for conveyance to the pump and valve actuators on the pistonelement 102.

By operating three way valve C6, the positive pressure can also bedirected to fill the occluder bladder 152. When the valve C6 is in thisposition, the positive pressure in the occluder bladder 152 also can beconveyed to the pump and valve actuators on the piston element 102.

Otherwise, valve C6 directs the positive pressure through the bypassline 228 to the vent 158. In the absence of an electrical signal (forexample, if there is a power failure), valve C6 opens the occluderbladder 152 to the bypass line 228 to the vent 158.

Valve A6 is either opened to convey air in the main branch line 216 tothe low pressure reservoir 214 or closed to block this conveyance. Thetransducer XLPOS opens the valve A6 upon sensing a pressure below thelow-relative cut-off. The transducer XLPOS closes the valve station A6upon sensing pressure above the low-relative cut-off.

The transducer XHIPOS operates valve C5 to close communication betweenthe pump outlet line 210 and the main positive branch line 216 uponsensing a pressure above the high-relative cut-off of 7.5 psig.

In the third mode, valve D0 closes communication between the negativebranch line 212 and the pump inlet line 208. Valve C5 openscommunication between the pump outlet line 210 and the vent 158, whileblocking communication with the main positive branch line 216.

The pump 84 operates to circulate air in a loop from the vent 158through its inlet and outlet lines 208/210 back to the vent 158.

b. The Pressure Actuating Network

As FIG. 24 shows, the regulation system also includes first and secondpressure actuating networks 230 and 232.

The first pressure actuating network 230 distributes negative andpositive pressures to the first pump actuator PA1 and the valveactuators that serve it (namely, VA1; VA2; VA8; VA9; and VA10). Theseactuators, in turn, operate cassette pump station P1 and valve stationsV1; V2; V8; V9; and V10, respectively, which serve pump station P1.

The second pressure actuating network 232 distributes negative andpositive pressures to the second pump actuator PA2 and the valveactuators that serve it (namely, VA3; VA4; VA5; VA6; and VA7). Theseactuators, in turn, operate cassette pump station P2 and cassette valvestations V3; V4; V5; V6; and V7, which serve pump station P2.

The controller 16 can operate the first and second actuating networks230 and 232 in tandem to alternately fill and empty the pump chambers P1and P2. This provides virtually continuous pumping action through thecassette 24 from the same source to the same destination.

Alternatively, the controller 16 can operate the first and secondactuating networks 230 and 232 independently. In this way, thecontroller 16 can provide virtually simultaneous pumping action throughthe cassette 24 between different sources and different destinations.

This simultaneous pumping action can be conducted with eithersynchronous or non-synchronous pressure delivery by the two networks 230and 232. The networks 230 and 232 can also be operated to providepressure delivery that drifts into an out of synchronousness.

The first actuating network 230 provides high-relative positive pressureand negative pressures to the valve actuators VA1; VA2; VA8; VA9; andVA10.

The first actuating network 230 also selectively provides eitherhigh-relative positive and negative pressure or low-relative positiveand negative pressure to the first pumping actuator PA1.

Referring first to the valve actuators, three way valves C0; C1; C2; C3;and C4 in the manifold assembly 162 control the flow of high-relativepositive pressure and negative pressures to the valve actuators VA1;VA2; VA8; VA9; and VA10.

The high-relative positive pressure region of the main branch line 216communicates with the valves C0; C1: C2; C3; and C4 through a bridgeline 234, a feeder line 236, and individual connecting lines 238.

The negative pressure branch 212 communicates with the valves C0; C1;C2; C3; and C4 through individual connecting lines 340. The controller16 sets this branch 212 to a high-relative negative pressure conditionby setting the transducer XNEG sense a high-relative pressure cut-off.

By applying negative pressure to one or more given valve actuators, theassociated cassette valve station is opened to accommodate liquid flow.By applying positive pressure to one or more given valve actuators, theassociated cassette value station is closed to block liquid flow. Inthis way, the desired liquid path leading to and from the pump chamberP1 can be selected.

Referring now to the pump actuator PA1, two way valve A4 in the manifoldassembly 162 communicates with the high-relative pressure feeder line236 through connecting line 342. Two way valve A3 in the manifoldassembly 162 communicates with the low-relative positive pressurereservoir through connecting line 344. By selectively operating eithervalve A4 or A3, either high-relative or low-relative positive pressurecan be supplied to the pump actuator PA1.

Two way valve A0 communicates with the negative pressure branch 212through connecting line 346. By setting the transducer XNEG to senseeither a low-relative pressure cut-off or a high-relative pressurecut-off, either low-relative or high-relative pressure can be suppliedto the pump actuator VA1 by operation of valve A0.

By applying negative pressure (through valve A0) to the pump actuatorPA1, the cassette diaphragm 59 flexes out to draw liquid into the pumpchamber P1. By applying positive pressure (through either valve A3 orA4) to the pump actuator PA1, the cassette diaphragm 59 flexes in topump liquid from the pump chamber P1 (provided, of course, that theassociated inlet and outlet valves are opened). By modulating the timeperiod during which pressure is applied, the pumping force can bemodulated between full strokes and partial strokes with respect to thepump chamber P1.

The second actuating network 232 operates like the first actuatingnetwork 230, except it serves the second pump actuator PA2 and itsassociated valve actuators VA3; VA4; VA5; VA6; and VA7.

Like the first actuating network 230, the second actuating network 232provides high-relative positive pressure and high-relative negativepressures to the valve actuators VA3; VA4; VA5; VA6; and VA7. Three wayvalves D1; D2: D3; D4; and D5 in the manifold assembly 162 control theflow of high-relative positive pressure and high-relative negativepressures to the valve actuators VA3; VA4; VA5; VA6; and VA7.

The high-relative positive pressure region 222 of the main branch linecommunicates with the valves D1; D2; D3; D4; and D5 through the bridgeline 234, the feeder line 236, and connecting lines 238.

The negative pressure branch 212 communicates with the valves D1: D2;D3; D4; and D5 through connecting lines 340. This branch 212 can be setto a high-relative negative pressure condition by setting the transducerXNEG to sense a high-relative pressure cut-off.

Like the first actuating network 230, the second actuating network 232selectively provides either high-relative positive and negative pressureor low-relative positive and negative pressure to the second pumpingactuator PA2. Two way valve B0 in the manifold assembly 162 communicateswith the high-relative pressure feeder line through connecting line 348.Two way valve station B1 in the manifold assembly 162 communicates withthe low-relative positive pressure reservoir through connecting line349. By selectively operating either valve B0 or B1, eitherhigh-relative or low-relative positive pressure can be supplied to thepump actuator PA2.

Two way valve B4 communicates with the negative pressure branch throughconnecting line 350. By setting the transducer XNEG to sense either alow-relative pressure cut-off or a high-relative pressure cut-off,either low-relative or high-relative pressure can be supplied to thepump actuator PA2 by operation of valve B4.

Like the first actuating network 230, by applying negative pressure toone or more given valve actuators, the associated cassette value stationis opened to accommodate liquid flow. By applying positive pressure toone or more given valve actuators, the associated cassette value stationis closed to block liquid flow. In this way, the desired liquid pathleading to and from the pump chamber P2 can be selected.

By applying a negative pressure (through valve B4) to the pump actuatorPA2, the cassette diaphragm flexes out to draw liquid into the pumpchamber P2. By applying a positive pressure (through either valve BB0 orB1) to the pump actuator PA2, the cassette diaphragm flexes in to moveliquid from the pump chamber P2 (provided, of course, that theassociated inlet and outlet valves are opened). By modulating the timeperiod during which pressure is applied, the pumping force can bemodulated between full strokes and partial strokes with respect to thepump chamber P2.

The first and second actuating networks 230/232 can operate insuccession, one drawing liquid into pump chamber P1 while the other pumpchamber P2 pushes liquid out of pump chamber P2, or vice versa, to moveliquid virtually continuously from the same source to the samedestination.

The first and second actuating networks 230/232 can also operate tosimultaneously move one liquid through pump chamber P1 while movinganother liquid through pump chamber P2. The pump chambers P1 and P2 andserve the same or different destinations.

Furthermore, with additional reservoirs, the first and second actuationnetworks 232/232 can operate on the same or different relative pressureconditions. The pump chamber P1 can be operated with low-relativepositive and negative pressure, while the other pump chamber P2 isoperated with high-relative positive and negative pressure.

c. Liquid Volume Measurement

As FIG. 24 shows, the pressure regulating system 200 also includes anetwork 350 that works in conjunction with the controller 16 formeasuring the liquid volumes pumped through the cassette.

The liquid volume measurement network 350 includes a reference chamberof known air volume (V_(S)) associated with each actuating network.Reference chamber VS1 is associated with the first actuating network.Reference chamber VS2 is associated with the second actuating network.

The reference chambers VS1 and VS2 may be incorporated at part of themanifold assembly 162, as FIG. 20 shows.

In a preferred arrangement (as FIG. 14B shows), the reference chambersVS1 and VS2 are carried by the piston element 102' itself, or at anotherlocated close to the pump actuators PA1 and PA2 within the cassetteholder 100.

In this way, the reference chambers VS1 and VS2, like the pump actuatorsPA1 and PA2, exposed to generally the same temperature conditions as thecassette itself.

Also in the illustrated and preferred embodiment, inserts 117 occupy thereference chambers VS1 and VS2. Like the inserts 117 carried within thepump actuators PA1 and PA2, the reference chamber inserts 117 are madeof an open cell foam material. By dampening and directing theapplication of pneumatic pressure, the reference chamber inserts 117make measurement of air volumes faster and less complicated.

Preferably, the insert 117 also includes a heat conducting coating ormaterial to help conduct heat into the reference chamber VS1 and VS2. Inthe illustrated embodiment, a thermal paste is applied to the foaminsert.

This preferred arrangement minimizes the effects of temperaturedifferentials upon liquid volume measurements.

Reference chamber VS1 communicates with the outlets of valves A0; A3;and A4 through a normally closed two way valve A2 in the manifoldassembly 162. Reference chamber VS1 also communicates with a vent 352through a normally closed two way valve A1 in the manifold assembly 162.

Transducer XVS1 in the manifold assembly 162 senses the amount of airpressure present within the reference chamber VS1. Transducer XP1 sensesthe amount of air pressure present in the first pump actuator PA1.

Likewise, reference chamber VS2 communicates with the outlets of valveB0; B1; and B4 through a normally closed two way valve B2 in themanifold assembly 162. Reference chamber VS2 also communicates with afiltered vent 356 through a normally closed two way valve B3 in themanifold assembly 162.

Transducer XVS2 in the manifold assembly 162 senses the amount of airpressure present within the reference chamber VS2. Transducer XP2 sensesthe amount of air pressure present in the second pump actuator PA2.

The controller 16 operates the network 350 to perform an air volumecalculation twice, once during each draw (negative pressure) cycle andonce again during each pump (positive pressure) cycle of each pumpactuator PA1 and PA2.

The controller 16 operates the network 350 to perform the first airvolume calculation after the operating pump chamber is filled with theliquid to be pumped (i.e., after its draw cycle). This provides aninitial air volume (V_(i)).

The controller 16 operates the network 350 to perform the second airvolume calculation after moving fluid out of the pump chamber (i.e.,after the pump cycle). This provides a final air volume (V_(f)).

The controller 16 calculates the difference between the initial airvolume V_(i) and the final air volume V_(f) to derive a delivered liquidvolume (V_(d)), where:

    V.sub.d =V.sub.f -V.sub.i

The controller 16 accumulates V_(d) for each pump chamber to derivetotal liquid volume pumped during a given procedure. The controller 16also applies the incremental liquid volume pumped over time to deriveflow rates.

The controller 16 derives V_(i) in this way (pump chamber P1 is used asan example):

(1) The controller 16 actuates the valves C0 to C4 to close the inletand outlet passages leading to the pump chamber P1 (which is filled withliquid). Valves A2 and A1 are normally closed, and they are kept thatway.

(2) The controller 16 opens valve A1 to vent reference chamber VS1 toatmosphere. The controller 16 then conveys positive pressure to the pumpactuator PA1, by opening either valve A3 (low-reference) or A4(high-reference), depending upon the pressure mode selected for the pumpstroke.

(3) The controller 16 closes the vent valve A1 and the positive pressurevalve A3 or A4, to isolate the pump chamber PA1 and the referencechamber VS1.

(4) The controller 16 measures the air pressure in the pump actuator PA1(using transducer XP1) (IP_(d1)) and the air pressure in the referencechamber VS1 (using transducer XVS1) (IP_(s1)).

(5) The controller 16 opens valve A2 to allow the reference chamber VS1to equilibrate with the pump chamber PA1.

(6) The controller 16 measures the new air pressure in the pump actuatorPA1 (using transducer XP1) (IP_(d2)) and the new air pressure in thereference chamber (using transducer XVS1) (IP_(s2)).

(7) The controller 16 closes the positive pressure valve A3 or A4.

(8) The controller 16 calculates initial air volume V_(i) as follows:##EQU1##

After the pump chamber P1 is emptied of liquid, the same sequence ofmeasurements and calculations are made to derive V_(f), as follows:

(9) Keeping valve stations A2 and A1 closed, the controller 16 actuatesthe valves C0 to C4 to close the inlet and outlet passages leading tothe pump chamber P1 (which is now emptied of liquid).

(10) The controller 16 opens valve A1 to vent reference chamber VS1 toatmosphere, and then conveys positive pressure to the pump actuator PA1,by opening either valve A3 (low-reference) or A4 (high-reference),depending upon the pressure mode selected for the pump stroke.

(11) The controller 16 closes the vent valve A1 and the positivepressure valve A3 or A4, to isolate the pump actuator PA1 and thereference chamber VS1.

(12) The controller 16 measures the air pressure in the pump actuatorPA1 (using transducer XP1) (FP_(d1)) and the air pressure in thereference chamber VS1 (using transducer XVS1) (FP_(s1)).

(13) The controller 16 opens valve A2, allowing the reference chamberVS1 to equilibrate with the pump actuator.

(14) The controller 16 measures the new air pressure in the pumpactuator PA1 (using transducer XP1) (FP_(d2)) and the new air pressurein the reference chamber (using transducer XVS1) (FP_(s2)).

(15) The controller 16 closes the positive pressure valve A3 or A4.

(16) The controller 16 calculates final air volume V_(f) as follows:##EQU2##

The liquid volume delivered (V_(d)) during the preceding pump stroke is:

    V.sub.d =V.sub.f -V.sub.i

Preferably, before beginning another pump stroke, the operative pumpactuator is vented to atmosphere (by actuating valves A2 and A1 for pumpactuator PA1, and by actuating valves B2 and B3 for pump actuator PA2).

The controller 16 also monitors the variation of V_(d) over time todetect the presence of air in the cassette pump chamber P1/P2. Airoccupying the pump chamber P1/P2 reduces the capacity of the chamber tomove liquid. If V_(d) decrease over time, or if V_(d) falls below a setexpected value, the controller 16 attributes this condition to thebuildup of air in the cassette chamber.

When this condition occurs, the controller 16 conducts an air removalcycle, in which liquid flow through the affected chamber is channeledthrough the top portion of the chamber to the drain or to the heater bagfor a period of time. The air removal cycle rids the chamber of excessair and restores V_(d) to expected values.

In another embodiment, the controller 16 periodically conducts an airdetection cycle. In this cycle, the controller 16 delivers fluid into agiven one of the pump chambers P1 and P2. The controller 16 then closesall valve stations leading into and out of the given pump chamber, tothereby trap the liquid within the pump chamber.

The controller 16 then applies air pressure to the actuator associatedwith the pump chamber and derives a series of air volume V_(i)measurements over a period of time in the manner previously disclosed.Since the liquid trapped within the pump chamber is relativelyincompressible, there should be virtually no variation in the measuredV_(i) during the time period, unless there is air present in the pumpchamber. If V_(i) does vary over a prescribed amount during the timeperiod, the controller 16 contributes this to the presence of air in thepump chamber.

When this condition occurs, the controller 16 conducts an air removalcycle in the manner previously described.

The controller 16 performs the liquid volume calculations assuming thatthe temperature of the reference chamber VS1/VS2 does not differsignificantly from the temperature of the pump chamber P1/P2.

One way to minimize any temperature difference is to mount the referencechamber as close to the pump chamber as possible. FIG. 14B shows thispreferred alternative, where the reference chamber is physically mountedon the piston head 116.

Temperature differences can also be accounted for by applying atemperature correction factor (F_(t)) to the known air volume of thereference chamber V_(s) to derive a temperature-corrected reference airvolume V_(st), as follows:

    V.sub.st =F.sub.t *V.sub.S

where:

    F.sub.t =C.sub.t /R.sub.t

and where:

C_(t) is the absolute temperature of the cassette (expressed in degreesRankine or Kelvin), and

R_(t) is the temperature of the reference chamber (expressed in the sameunits as C_(t)).

In this embodiment, the network substitutes V_(st) for V_(s) in theabove volume derivation calculations.

The value of F_(t) can be computed based upon actual, real timetemperature calculations using temperature sensors associated with thecassette and the reference chamber.

Because liquid volume measurements are derived after each pumpingstroke, the same accuracy is obtained for each cassette loaded into thecycler, regardless of variations in tolerances that may exist among thecassettes used.

III. THE CYCLER CONTROLLER 16

FIGS. 9; 10; 17; and 18 show the cycler controller 16.

The controller 16 carries out process control and monitoring functionsfor the cycler 14. The controller 16 includes a user interface 367 witha display screen 370 and keypad 368. The user interface 367 receivescharacters from the keypad 368, displays text to a display screen 370,and sounds the speaker 372 (shown in FIGS. 9 and 10). The interface 367presents status information to the user during a therapy session. Theinterface 367 also allows the user to enter and edit therapy parameters,and to issue therapy commands.

In the illustrated embodiment, the controller 16 comprises a centralmicroprocessing unit (CPU) 358. The CPU is etched on the board 184carried on stand off pins 182 atop the second module 88. Power harnesses360 link the CPU 358 to the power supply 90 and to the operativeelements of the manifold assembly 162.

The CPU 358 employs conventional real-time multi-tasking to allocate CPUcycles to application tasks. A periodic timer interrupt (for example,every 10 milliseconds) preempts the executing task and schedules anotherthat is in a ready state for execution. If a reschedule is requested,the highest priority task in the ready state is scheduled. Otherwise,the next task on the list in the ready state is scheduled.

The following provides an overview of the operation of the cycler 14under the direction of the controller CPU 358.

(A) The User Interface

1. System Power Up/MAIN MENU (FIG. 25)

When power is turned on, the controller 16 runs through anINITIALIZATION ROUTINE.

During the initialization routine, the controller 16 verifies that itsCPU 358 and associated hardware are working. If these power-up testsfail, the controller 16 enters a shutdown mode.

If the power-up tests succeed, the controller 16 loads the therapy andcycle settings saved in non-volatile RAM during the last power-down. Thecontroller 16 runs a comparison to determine whether these settings, asloaded, are corrupt.

If the therapy and cycle settings loaded from RAM are not corrupt, thecontroller 16 prompts the user to press the GO key to begin a therapysession.

When the user presses the GO key, the controller 16 displays the MAINMENU. The MAIN MENU allows the user to choose to (a) select the therapyand adjust the associated cycle settings; (b) review the ultrafiltratefigures from the last therapy session, and (c) start the therapy sessionbased upon the current settings.

2. THERAPY SELECTION MENU (FIG. 26)

With choice (a) of the MAIN MENU selected, the controller 16 displaysthe THERAPY SELECTION MENU. This menu allows the user to specify the APDmodality desired, selecting from CCPD, IPD, and TPD (with an withoutfull drain phases).

The user can also select an ADJUST CYCLE SUBMENU. This submenu allowsthe user to select and change the therapy parameters.

For CCPD and IPD modalities, the therapy parameters include the THERAPYVOLUME, which is the total dialysate volume to be infused during thetherapy session (in ml); the THERAPY TIME, which is the total timeallotted for the therapy (in hours and minutes); the FILL VOLUME, whichis the volume to be infused during each fill phase (in ml), based uponthe size of the patient's peritoneal cavity; the LAST FILL VOLUME, whichis the final volume to be left in the patient at the end of the session(in ml); and SAME DEXTROSE (Y OR N), which allows the user to specify adifferent dextrose concentration for the last fill volume.

For the TPD modality, the therapy parameters include THERAPY VOLUME,THERAPY TIME, LAST FILL VOLUME, AND SAME DEXTROSE (Y OR N), as abovedescribed. In TPD, the FILL VOLUME parameter is the initial tidal fillvolume (in ml). TPD includes also includes as additional parametersTIDAL VOLUME PERCENTAGE, which is the fill volume to be infused anddrained periodically, expressed as a percentage of the total therapyvolume; TIDAL FULL DRAINS, which is the number of full drains in thetherapy session; and TOTAL UF, which is the total ultrafiltrate expectedfrom the patient during the session (in ml), based upon prior patientmonitoring.

The controller 16 includes a THERAPY LIMIT TABLE. This Table setspredetermined maximum and minimum limits and permitted increments forthe therapy parameters in the ADJUST CYCLE SUBMENU.

The controller 16 also includes a THERAPY VALUE VERIFICATION ROUTINE.This routine checks the parameters selected to verify that a reasonabletherapy session has been programmed. The THERAPY VALUE VERIFICATIONROUTINE checks to assure that the selected therapy parameters include adwell time of at least one minute; at least one cycle; and for TPD theexpected filtrate is not unreasonably large (i.e., it is less than 25%of the selected THERAPY VOLUME). If any of these parameters isunreasonable, the THERAPY VALUE VERIFICATION ROUTINE places the userback in the ADJUST CYCLE SUBMENU and identifies the therapy parameterthat is most likely to be wrong. The user is required to program areasonable therapy before leaving the ADJUST CYCLE SUBMENU and begin atherapy session.

Once the modality is selected and verified, the controller 16 returns touser to the MAIN MENU.

3. REVIEW ULTRAFILTRATION MENU

With choice (b) of the MAIN MENU selected, the controller 16 displaysthe REVIEW ULTRAFILTRATION MENU (see FIG. 25).

This Menu displays LAST UF, which is the total volume of ultrafiltrategenerated by the pervious therapy session. For CCPD and IPD modalities,the user can also select to ULTRAFILTRATION REPORT. This Report providesa cycle by cycle breakdown of the ultrafiltrate obtained from theprevious therapy session.

4. SET-UP PROMPTS/LEAK TESTING

With choice (c) of the MAIN MENU selected, the controller 16 firstdisplays SET-UP PROMPTS to the user (as shown in FIG. 27).

The SET-UP PROMPTS first instruct the user to LOAD SET. The user isrequired to open the door; load a cassette; close the door; and press GOto continue with the set-up dialogue.

When the user presses GO, the controller 16 pressurizes the main bladderand occluder bladder and tests the door seal.

If the door seal fails, the controller 16 prompts the user to try again.If the door continues to fail a predetermined period of times, thecontroller 16 raises a SYSTEM ERROR and shuts down.

If the door seal is made, the SET-UP PROMPTS next instruct the user toCONNECT BAGS. The user is required to connect the bags required for thetherapy session; to unclamp the liquid tubing lines being use and assurethat the liquid lines that are not remained clamped (for example, theselected therapy may not require final fill bags, so liquid lines tothese bags should remain clamped). Once the user accomplishes thesetasks, he/she presses GO to continue with the set-up dialogue.

When GO is pressed, the controller 16 checks which lines are clamped anduses the programmed therapy parameters to determine which lines shouldbe primed. The controller 16 primes the appropriate lines. Primingremoves air from the set lines by delivering air and liquid from eachbag used to the drain.

Next, the controller 16 performs a predetermined series of integritytests to assure that no valves in the cassette leak; that there are noleaks between pump chambers; and that the occluder assembly stops allliquid flow.

The integrity tests first convey the predetermined high-relativenegative air pressure (-5.0 psig) to the valve actuators VA1 to VA10.The transducer XNEG monitors the change in high-relative negative airpressure for a predetermined period. If the pressure change over theperiod exceeds a predetermined maximum, the controller 16 raises aSYSTEM ERROR and shuts down.

Otherwise, the integrity tests convey the predetermined high-relativepositive pressure (7.0 psig) to the valve actuators VA1 to VA10. Thetransducer XHPOS monitors the change in high-relative positive airpressure for a predetermined period. If the pressure change over theperiod exceeds a predetermined maximum, the controller 16 raises aSYSTEM ERROR and shuts down.

Otherwise, the integrity tests proceed. The valve actuators VA1 to VA10convey positive pressure to close the cassette valve stations V1 to V10.The tests first convey the predetermined maximum high-relative negativepressure to pump actuator PA1, while conveying the predetermined maximumhigh-relative positive pressure to pump actuator PA2. The transducersXP1 and XP2 monitor the pressures in the respective pump actuators PA1and PA2 for a predetermined period. If pressure changes over the periodexceed a predetermined maximum, the controller 16 raises a SYSTEM ERRORand shuts down.

Otherwise, the tests next convey the predetermined maximum high-relativepositive pressure to pump actuator PA1, while conveying thepredetermined maximum high-relative negative pressure to pump actuatorPA2. The transducers XP1 and XP2 monitor the pressures in the respectivepump actuators PA1 and PA2 for a predetermined period. If pressurechanges over the period exceed a predetermined maximum, the controller16 raises a SYSTEM ERROR and shuts down.

Otherwise, power to valve C6 is interrupted. This vents the occluderbladder 152 and urges the occluder blade and plate 144/148 together,crimping cassette tubing 26 to 34 closed. The pump chambers P1 and P2are operated at the predetermined maximum pressure conditions and liquidvolume measurements taken in the manner previously described. If eitherpump chamber P1/P2 moves liquid pass the closed occluder blade and plate144/148, the controller 16 raises a SYSTEM ERROR and shuts down.

If all integrity tests succeed, the SET-UP PROMPTS next instruct theuser to CONNECT PATIENT. The user is required to connect the patientaccording to the operator manual and press GO to begin the dialysistherapy session selected.

The controller 16 begins the session and displays the RUN TIME MENU.

5. RUN TIME MENU

Attention is now directed to FIG. 28.

The RUN TIME MENU is the active therapy interface. The RUN TIME MENUprovides an updated real-time status report of the current progress ofthe therapy session.

The RUN TIME MENU includes the CYCLE STATUS, which identifies the totalnumber of fill/dwell/drain phases to be conducted and the present numberof the phase underway (e.g., Fill 3 of 10); the PHASE STATUS, whichdisplays the present fill volume, counting up from 0 ml; theULTRAFILTRATION STATUS, which displays total ultrafiltrate accumulatedsince the start of the therapy session; the TIME, which is the presenttime; and FINISH TIME, which is the time that the therapy session isexpected to end.

Preferably, the user can also select in the RUN TIME MENU anULTRAFILTRATION STATUS REVIEW SUBMENU, which displays a cycle by cyclebreakdown of ultrafiltration accumulated.

From the RUN TIME MENU, the user can also select to STOP. The controller16 interrupts the therapy session and displays the STOP SUBMENU. TheSTOP SUBMENU allows the user to REVIEW the programmed therapy parametersand make change to the parameters; to END the therapy session; toCONTINUE the therapy session; to BYPASS the present phase; to conduct aMANUAL DRAIN; or ADJUST the intensity of the display and loudness ofalarms.

REVIEW restricts the type of changes that the user can make to theprogrammed parameters. For example, in REVIEW, the user cannot adjustparameters above or below a maximum specified amounts.

CONTINUE returns the user to the RUN TIME MENU and continue the therapysession where it left off.

The controller 16 preferably also includes specified time-outs for theSTOP SUBMENU. For example, if the user does not take any action in theSTOP SUBMENU for 30 minutes, the controller 16 automatically executesCONTINUE to return to the RUN TIME MENU and continue the therapysession. If the user does not take any action for 2 minutes afterselecting REVIEW, the controller 16 also automatically executesCONTINUE.

6. Background Monitoring Routine/System Errors

The controller 16 includes a BACKGROUND MONITORING ROUTINE that verifiessystem integrity at a predetermined intervals during the therapy session(e.g., every 10 seconds) (as FIG. 29 shows).

The BACKGROUND MONITORING ROUTINE includes

BAG OVER TEMP, which verifies that the heater bag is not too hot (e.g.,not over 44 degrees C.);

DELIVERY UNDER TEMP, which verifies that the liquid delivered to thepatient is not too cold (e.g., less than 33 degrees C.);

DELIVERY OVER TEMP, which verifies that the liquid delivered to thepatient is not too hot (e.g., over 38 degrees C.);

MONITOR TANKS, which verifies that the air tanks are at their operatingpressures (e.g., positive tank pressure at 7.5 psi +/-0.7 psi; patienttank at 5.0 psi +/-0.7 psi, except for heater to patient line, which is1.5 psi +/-0.2 psi; negative tank pressure at -5.0 psi +/-0.7 psi,except for patient to drain line, which is at -0.8 psi +/-0.2 psi);

CHECK VOLTAGES, which verify that power supplies are within their noiseand tolerance specs;

VOLUME CALC, which verifies the volume calculation math; and

CHECK CPU, checks the processor and RAM.

When the BACKGROUND MONITORING ROUTINE senses an error, the controller16 raises a SYSTEM ERROR. Loss of power also raises a SYSTEM ERROR. WhenSYSTEM ERROR occurs, the controller 16 sounds an audible alarm anddisplays a message informing the user about the problem sensed.

When SYSTEM ERROR occurs, the controller 16 also shuts down the cycler14. During shut down, the controller 16 ensures that all liquid deliveryis stopped, activates the occluder assembly, closes all liquid and airvalves, turns the heater plate elements off. If SYSTEM ERROR occurs dueto power failure, the controller 16 also vents the emergency bladder,releasing the door.

7. SELF-DIAGNOSTICS AND TROUBLE SHOOTING

According to the invention, the controller 16 monitors and controlspneumatic pressure within the internal pressure distribution system 86.Based upon pneumatic pressure measurements, the controller 16 calculatesthe amount and flow rate of liquid moved. The controller does notrequire an additional external sensing devices to perform any of itscontrol or measurement functions.

As a result, the system 10 requires no external pressure, weight, orflow sensors for the tubing 26 to 34 or the bags 20/22 to monitor anddiagnose liquid flow conditions. The same air pressure that moves liquidthrough the system 10 also serves to sense and diagnose all relevantexternal conditions affecting liquid flow, like an empty bag condition,a full bag condition, and an occluded line condition.

Moreover, strictly by monitoring the pneumatic pressure, the controller16 is able to distinguish a flow problem emanating from a liquid sourcefrom a flow problem emanating from a liquid destination.

Based upon the liquid volume measurements derived by the measurementnetwork 350, the controller 16 also derives liquid flow rate. Based uponvalues and changes in derived liquid flow rate, the controller 16 candetect an occluded liquid flow condition. Furthermore, based uponderived liquid flow rates, the controller can diagnose and determine thecause of the occluded liquid flow condition.

The definition of an "occluded flow" condition can vary depending uponthe APD phase being performed. For example, in a fill phase, an occludedflow condition can represent a flow rate of less than 20 ml/min. In adrain phase, the occluded flow condition can represent a flow rate ofless than 10 ml/min. In a bag to bag liquid transfer operation, anoccluded flow condition can represent a flow rate of less than 25ml/min. Occluded flow conditions for pediatric APD sessions can beplaced at lower set points.

When the controller 16 detects an occluded flow condition, it implementsthe following heuristic to determine whether the occlusion isattributable to a given liquid source or a given liquid destination.

When the controller 16 determines that the cassette cannot draw liquidfrom a given liquid source above the occluded flow rate, the controller16 determines whether the cassette can move liquid toward the sourceabove the occluded flow rate (i.e., it determines whether the liquidsource can serve as a liquid destination). If it can, the controller 16diagnoses the condition as an empty liquid source condition.

When the controller 16 determines that the cassette cannot push liquidtoward a given destination above the occluded flow rate, it determineswhether the cassette can draw liquid from the destination above theoccluded flow rate (i.e., it determines whether the liquid destinationcan serve as a liquid source). If it can, the controller diagnoses thecondition as being a full liquid destination condition.

When the controller 16 determines that the cassette can neither draw orpush liquid to or from a given source or destination above the occludedflow rate, the controller 16 interprets the condition as an occludedline between the cassette and the particular source or destination.

In this way, the system 10 operates by controlling pneumatic fluidpressure, but not by reacting to external fluid or liquid pressure orflow sensing.

8. ALARMS

With no SYSTEM ERRORS, the therapy session automatically continuesunless the controller 16 raises an ALARM1 or ALARM2. FIG. 30 shows theALARM1 and ALARM2 routines.

The controller 16 raises ALARM1 in situations that require userintervention to correct. The controller 16 raises ALARM1 when thecontroller 16 senses no supply liquid; or when the cycler 14 is notlevel. When ALARM1 occurs, the controller 16 suspends the therapysession and sounds an audible alarm. The controller 16 also displays anALARM MENU that informs the user about the condition that should becorrected.

The ALARM MENU gives the user the choice to correct the condition andCONTINUE; to END the therapy; or to BYPASS (i.e., ignore) the conditionand resume the therapy session.

The controller 16 raises ALARM2 in situations that are anomalies butwill typically correct themselves with minimum or no user intervention.For example, the controller 16 raises ALARM2 when the controller 16initially senses a low flow or an occluded lines. In this situation, thepatient might have rolled over onto the catheter and may need only tomove to rectify the matter.

When ALARM2 occurs, the controller 16 generates a first audible signal(e.g., 3 beeps). The controller 16 then mutes the audible signal for 30seconds. If the condition still exists after 30 second, the controller16 generates a second audible signal (e.g., 8 beeps) The controller 16again mutes the audible signal. If the condition still exists 30 secondslater, the controller 16 raises an ALARM1, as described above. The useris then required to intervene using the ALARM MENU.

9. POST THERAPY PROMPTS

The controller 16 terminates the session when (a) the prescribed therapysession is successfully completed; (b) the user selects END in the STOPSUBMENU or the ALARM MENU; or (c) a SYSTEM ERROR condition occurs (seeFIG. 31).

When any of these events occur, the controller 16 displays POST THERAPYPROMPTS to the user. The POST THERAPY PROMPTS inform the user THERAPYFINISHED, to CLOSE CLAMPS, and to DISCONNECT PATIENT. The user pressesGO to advance the prompts.

Once the user disconnects the patient and presses GO, the controller 16displays PLEASE WAIT and depressurizes the door. Then the controller 16then directs the user to REMOVE SET.

Once the user removes the set and presses GO, the controller 16 returnsto user to the MAIN MENU.

(B) Controlling an APD Therapy Cycle

1. Fill Phase

In the fill phase of a typical three phase APD cycle, the cycler 14transfers warmed dialysate from the heater bag 22 to the patient.

The heater bag 22 is attached to the first (uppermost) cassette port 27.The patient line 34 is attached to the fifth (bottommost) cassette port35.

As FIG. 32 shows, the fill phase involves drawing warmed dialysate intocassette pump chamber P1 through primary liquid path F1 via branchliquid path F6. Then, pump chamber P1 expels the heated dialysatethrough primary liquid path F5 via branch liquid path F8.

To expedite pumping operations, the controller 16 preferably works pumpchamber P2 in tandem with pump chamber P1. The controller 16 drawsheated dialysate into pump chamber P2 through primary liquid path F1 viabranch liquid path F7. Then, pump chamber P2 expels the heated dialysatethrough primary liquid path F5 through branch liquid path F9.

The controller 16 works pump chamber P1 in a draw stroke, while workingpump chamber P2 in a pump stroke, and vice versa.

In this sequence, heated dialysate is always introduced into the topportions of pump chambers P1 and P2. The heated dialysate is alwaysdischarged through the bottom portions of pump chambers P1 and P2 to thepatient free of air.

Furthermore, during liquid transfer directly with the patient, thecontroller 16 can supply only low-relative positive and negativepressures to the pump actuators PA1 and PA2.

In carrying out this task, the controller 16 alternates the followingsequences 1 and 2:

1. Perform pump chamber P1 draw stroke (drawing a volume of heateddialysate into pump chamber P1 from the heater bag), while performingpump chamber P2 pump stroke (expelling a volume of heated dialysate frompump chamber P2 to the patient).

(i) Open inlet path F1 to pump chamber P1, while closing inlet path F1to pump chamber P2. Actuate valve C0 to supply high-relative negativepressure to valve actuator VA1, opening cassette valve station V1.Actuate valves C1; D1; and D2 to supply high-relative positive pressureto valve actuators VA2; VA3: and VA4, closing cassette valve station V2;V3; and V4.

(ii) Close outlet path F5 to pump chamber P1, while opening outlet pathF5 to pump chamber P2. Actuate valves C2 to C4 and D3 to D5 to supplyhigh-relative positive pressure to valve actuators VA8 to V10 and VA5 toVA7, closing cassette valve stations V8 to V10 and V5 to V7. Actuatevalve D5 to supply high-relative negative pressure to valve actuatorVA7, opening cassette valve station V7.

(iii) Flex the diaphragm underlying actuator PA1 out. Actuate valve A0to supply low-relative negative pressure to pump actuator PA1.

(iv) Flex the diaphragm underlying actuator PA2 in. Actuate valve B1 tosupply low-relative positive pressure to pump actuator PA2.

2. Perform pump chamber P2 draw stroke (drawing a volume of heateddialysate into pump chamber P2 from the heater bag), while performingpump chamber P1 pump stroke (expelling a volume of heated dialysate frompump chamber P1 to the patient).

(i) Open inlet path F1 to pump chamber P2, while closing inlet path F1to pump chamber P1. Actuate valves C0; C1; and D2 to supplyhigh-relative positive pressure to valve actuators VA1; VA2; and VA4,closing cassette valve stations V1; V2; and V4. Actuate valve D1 tosupply high-relative negative pressure to valve actuator VA3, openingcassette valve station V3.

(ii) Close outlet path F5 to pump chamber P2, while opening outlet pathF5 to pump chamber P1. Actuate valve C2 to supply high-relative negativepressure to valve actuator VA8, opening cassette valve station V8.Actuate valves D3 to D5; C2; and C4 to supply high-relative positivepressure to valve actuators VA5 to VA7; V9; and V10, closing cassettevalve stations V5 to V7; V9; and V10.

(iii) Flex the diaphragm underlying actuator PA1 in. Actuate valve A3 tosupply low-relative positive pressure to pump actuator PA1.

(iv) Flex the diaphragm underlying actuator PA2 out. Actuate valve B4 tosupply low-relative negative pressure to pump actuator PA2.

2. Dwell Phase

Once the programmed fill volume has been transferred to the patient, thecycler 14 enters the second or dwell phase. In this phase, the cycler 14replenishes the heater bag by supplying fresh dialysate from a sourcebag.

The heater bag is attached to the first (uppermost) cassette port. Thesource bag line is attached to the fourth cassette port, immediatelyabove the patient line.

As FIG. 33 shows, the replenish heater bag phase involves drawing freshdialysate into cassette pump chamber P1 through primary liquid path F4via branch liquid path F8. Then, pump chamber P1 expels the dialysatethrough primary liquid path F1 via branch liquid path F6.

To expedite pumping operations, the controller 16 preferably works pumpchamber P2 in tandem with pump chamber P1. The controller 16 draws freshdialysate into cassette pump chamber P2 through primary liquid path F4via branch liquid path F9. Then, pump chamber P2 expels the dialysatethrough primary liquid path F1 via branch liquid path F7.

The controller 16 works pump chamber P1 in a draw stroke, while workingpump chamber P2 in a pump stroke, and vice versa.

In this sequence, fresh dialysate is always introduced into the bottomportions of pump chambers P1 and P2. The fresh dialysate is alwaysdischarged through the top portions of pump chambers P1 and P2 to theheater bag. This allows entrapped air to be removed from the pumpchambers P1 and P2.

Furthermore, since liquid transfer does not occur directly with thepatient, the controller 16 supplies high-relative positive and negativepressures to the pump actuators PA1 and PA2.

In carrying out this task, the controller 16 alternates the followingsequences:

1. Perform pump chamber P1 draw stroke (drawing a volume of freshdialysate into pump chamber P1 from a source bag), while performing pumpchamber P2 pump stroke (expelling a volume of fresh dialysate from pumpchamber P2 to the heater bag).

(i) Open inlet path F4 to pump chamber P1, while closing inlet path F4to pump chamber P2. Actuate valve C3 to supply high-relative negativepressure to valve actuator VA9, opening cassette valve station V9.Actuate valves D3 to D5; C2; and C4 to supply high-relative positivepressure to valve actuators VA5 to VA8; and VA10, closing cassette valvestations V5 to V8 and V10.

(ii) Close outlet path F1 to pump chamber P1, while opening outlet pathF1 to pump chamber P2. Actuate valves C0; C1; and D2 to supplyhigh-relative positive pressure to valve actuators VA1; VA2 and VA4,closing cassette valve stations V1; V2; and V4. Actuate valve D1 tosupply high-relative negative pressure to valve actuator VA3, openingcassette valve station V3.

(iii) Flex the diaphragm underlying actuator PA1 out. Actuate valve A0to supply high-relative negative pressure to pump actuator PA1.

(iv) Flex the diaphragm underlying actuator PA2 in. Actuate valve B0 tosupply high-relative positive pressure to pump actuator PA2.

2. Perform pump chamber P2 draw stroke (drawing a volume of freshdialysate into pump chamber P2 from a source bag), while performing pumpchamber P1 pump stroke (expelling a volume of fresh dialysate from pumpchamber P1 to heater bag).

(i) Close inlet path F4 to pump chamber P1, while opening inlet path F4to pump chamber P2. Actuate valve D5 to supply high-relative negativepressure to valve actuator VA6, opening cassette valve station V6.Actuate valves C3 to C4; D3; and D5 to supply high-relative positivepressure to valve actuators VA5 and VA7 to VA10, closing cassette valvestations V5 and V7 to V10.

(ii) Open outlet path F1 to pump chamber P1, while closing outlet pathF1 to pump chamber P2. Actuate valve C0 to supply high-relative negativepressure to valve actuator VA1, opening cassette valve station V1.Actuate valves C1; D1; and D2 to supply high-relative positive pressureto valve actuators VA2 to VA4, closing cassette valve station V2 to V4.

(iii) Flex the diaphragm underlying actuator PA1 in. Actuate valve A4 tosupply high-relative positive pressure to pump actuator PA1.

(iv) Flex the diaphragm underlying actuator PA2 out. Actuate valve B4 tosupply high-relative relative negative pressure to pump actuator PA2.

3. Drain Phase

When the programmed drain phase ends, the cycler 14 enters the third ordrain phase. In this phase, the cycler 14 transfers spent dialysate fromthe patient to a drain.

The drain line is attached to the second cassette port. The patient lineis attached to the fifth, bottommost cassette port.

As FIG. 34 shows, the drain phase involves drawing spent dialysate intocassette pump chamber P1 through primary liquid path F5 via branchliquid path F8. Then, pump chamber P1 expels the dialysate throughprimary liquid path F2 via branch liquid path F6.

To expedite pumping operations, the controller 16 works pump chamber P2in tandem with pump chamber P1. The controller 16 draws spend dialysateinto cassette pump chamber P2 through primary liquid path F5 via branchliquid path F9. Then, pump chamber P2 expels the dialysate throughprimary liquid path F2 via branch liquid path F7.

The controller 16 works pump chamber P1 in a draw stroke, while workingpump chamber P2 in a pump stroke, and vice versa.

In this sequence, spent dialysate is always introduced into the bottomportions of pump chambers P1 and P2. The spent dialysate is alwaysdischarged through the top portions of pump chambers P1 and P2 to theheater bag. This allows air to be removed from the pump chambers P1 andP2.

Furthermore, since liquid transfer does occur directly with the patient,the controller 16 supplies low-relative positive and negative pressuresto the pump actuators PA1 and PA2.

In carrying out this task, the controller 16 alternates the followingsequences:

1. Perform pump chamber P1 draw stroke (drawing a volume of spentdialysate into pump chamber P1 from the patient), while performing pumpchamber P2 pump stroke (expelling a volume of spent dialysate from pumpchamber P2 to the drain).

(i) Open inlet path F5 to pump chamber P1, while closing inlet path F5to pump chamber Actuate valve C2 to supply high-relative negativepressure to valve actuator VA8, opening cassette valve station V8.Actuate valves D3 to D5, C3, and C4 to supply high-relative positivepressure valve actuators VA5 to VA7, VA9 and VA10, closing cassettevalve stations V5 to V7, V9, and V10.

(ii) Close outlet path F2 to pump chamber P1, while opening outlet pathF2 to pump chamber Actuate valves C0; C1; and D1 to supply high-relativepositive pressure to valve actuators VA1; VA2 and VA3, closing cassettevalve stations V1; and V3. Actuate valve D2 to supply high-relativenegative pressure to valve actuator VA4, opening cassette valve stationV4.

(iii) Flex the diaphragm underlying actuator PA1 out. Actuate valve A0to supply low-relative negative pressure to pump actuator PA1.

(iv) Flex the diaphragm underlying actuator PA2 in. Actuate valve B1 tosupply low relative positive pressure to pump actuator PA2.

2. Perform pump chamber P2 draw stroke (drawing a volume of spentdialysate into pump chamber P2 from the patient), while performing pumpchamber P1 pump stroke (expelling a volume of spent dialysate from pumpchamber P1 to the drain).

(i) Close inlet path F5 to pump chamber P1, while opening inlet path F5to pump chamber P2. Actuate valve D5 to supply high-relative negativepressure to valve actuator VA7, opening cassette valve station V7.Actuate valves D3; D4 and C2 to C4 to supply high-relative positivepressure to valve actuators VA5; VA6; and VA8 to VA10, closing cassettevalve stations V5, V6, and V8 to V10.

(ii) Open outlet path F2 to pump chamber P1, while closing outlet pathF2 to pump chamber P2. Actuate valve C1 to supply high-relative negativepressure to valve actuator VA2, opening cassette valve station V2.Actuate valves C0; D1; and D2 to supply high-relative positive pressureto valve actuators VA1; VA3; and VA4, closing cassette valve station V1;V3; and V4.

(iii) Flex the diaphragm underlying actuator PA1 in. Actuate valve A3 tosupply low-relative positive pressure to pump actuator PA1.

(iv) Flex the diaphragm underlying actuator PA2 out. Actuate valve B4 tosupply low-relative negative pressure to pump actuator PA2.

The controller 16 senses pressure using transducers XP1 and XP2 todetermine when the patient's peritoneal cavity is empty.

The drain phase is followed by another fill phase and dwell phase, aspreviously described.

4. Last Dwell Phase

In some APD procedures, like CCPD, after the last prescribedfill/dwell/drain cycle, the cycler 14 infuses a final fill volume. Thefinal fill volume dwells in the patient through the day. It is drainedat the outset of the next CCPD session in the evening. The final fillvolume can contain a different concentration of dextrose than the fillvolume of the successive CCPD fill/dwell/drain fill cycles the cycler 14provides. The chosen dextrose concentration sustains ultrafiltrationduring the day-long dwell cycle.

In this phase, the cycler 14 infuses fresh dialysate to the patient froma "last fill" bag. The "last fill" bag is attached to the third cassetteport. During the last swell phase, the heater bag is emptied, andsolution from last bag volume is transferred to the heater bag. Fromthere, the last fill solution is transferred to the patient to completethe last fill phase.

The last dwell phase involves drawing liquid from the heater bag intopump chamber P1 through primary liquid path F1 via branch path F6. The,the pump chamber P1 expels the liquid to the drain through primaryliquid path F2 via branch liquid path F6.

To expedite drainage of the heater bag, the controller 16 works pumpchamber P2 in tandem with pump chamber P1. The controller 16 drawsliquid from the heater bag into pump chamber P2 through primary liquidpath F1 via branch liquid path F7. Then, pump chamber P2 expels liquidto the drain through primary liquid path F2 via branch liquid path F7.

The controller 16 works pump chamber P1 in a draw stroke, while workingpump chamber P2 in a pump stroke, and vice versa.

Once the heater bag is drained, the controller 16 draws fresh dialysatefrom the "last fill" bag into cassette pump chamber P1 through primaryliquid path F3 via branch liquid path F8. Then, pump chamber P1 expelsthe dialysate to the heater bag through primary liquid path F1 via thebranch liquid path F6.

As before, to expedite pumping operations, the controller 16 preferablyworks pump chamber P2 in tandem with pump chamber P1. The controller 16draws fresh dialysate from the "last fill" bag into cassette pumpchamber P2 through primary liquid path F3 via branch liquid path F9.Then, pump chamber P2 expels the dialysate through primary liquid pathF1 via the branch liquid path F7.

The controller 16 works pump chamber P1 in a draw stroke, while workingpump chamber P2 in a pump stroke, and vice versa.

In this sequence, fresh dialysate from the "last fill" bag is alwaysintroduced into the bottom portions of pump chambers P1 and P2. Thefresh dialysate is always discharged through the top portions of pumpchambers P1 and P2 to the heater bag. This allows air to be removed fromthe pump chambers P1 and P2.

Furthermore, since liquid transfer does not occur directly with thepatient, the controller 16 can supply high-relative positive andnegative pressures to the pump actuators PA1 and PA2.

In carrying out this task, the controller 16 alternates the followingsequences (see FIG. 35):

1. Perform pump chamber P1 draw stroke (drawing a volume of freshdialysate into pump chamber P1 from the "last fill" bag), whileperforming pump chamber P2 pump stroke (expelling a volume of freshdialysate from pump chamber P2 to the heater bag).

(i) Open inlet path F3 to pump chamber P1, while closing inlet path F3to pump chamber P2. Actuate valve C4 to supply high-relative negativepressure to valve actuator VA10, opening cassette valve station V10.Actuate valves D3 to D5; C2; and C3 to supply high-relative positivepressure to valve actuators VA5 to VA9, closing cassette valve stationsV5 to V9.

(ii) Close outlet path F1 to pump chamber P1, while opening outlet pathF1 to pump chamber P2. Actuate valves C0; C1; and D2 to supplyhigh-relative positive pressure to valve actuators VA1; VA2 and VA4,closing cassette valve stations V1; V2; and V4. Actuate valve D1 tosupply high-relative negative pressure to valve actuator VA3, openingcassette valve station V3.

(iii) Flex the diaphragm underlying actuator PA1 out. Actuate valve A0to supply high-relative negative pressure to pump actuator PA1.

(iv) Flex the diaphragm underlying actuator PA2 in. Actuate valve B0 tosupply high-relative positive pressure to pump actuator PA2.

2. Perform pump chamber P2 draw stroke (drawing a volume of freshdialysate into pump chamber P2 from the "last fill" bag), whileperforming pump chamber P1 pump stroke (expelling a volume of freshdialysate from pump chamber P1 to heater bag).

(i) Close inlet path F3 to pump chamber P1, while opening inlet path F3to pump chamber P2. Actuate valve D3 to supply high-relative negativepressure to valve actuator VA5, opening cassette valve station V5.Actuate valves C2 to C4; D4; and D5 to supply high-relative positivepressure to valve actuators VA6 to VA10, closing cassette valve stationsV6 to V10.

(ii) Open outlet path F1 to pump chamber P1, while closing outlet pathF1 to pump chamber P2. Actuate valve C0 to supply high-relative negativepressure to valve actuator VA1, opening cassette valve station V1.Actuate valves C1; D1; and D2 to supply high-relative positive pressureto valve actuators VA2 to VA4, closing cassette valve station V2 to V4.

(iii) Flex the diaphragm underlying actuator PA1 in. Actuate valve A4 tosupply high-relative positive pressure to pump actuator PA1.

(iv) Flex the diaphragm underlying actuator PA2 out. Actuate valve B4 tosupply high-relative negative pressure to pump actuator PA2.

Once the last fill solution has been heated, it is transferred to thepatient in a fill cycle as described above (and as FIG. 32 shows).

According to one aspect of the invention, every important aspect of theAPD procedure is controlled by fluid pressure. Fluid pressure movesliquid through the delivery set, emulating gravity flow conditions basedupon either fixed or variable headheight conditions. Fluid pressurecontrols the operation of the valves that direct liquid among themultiple destinations and sources. Fluid pressure serves to seal thecassette within the actuator and provide a failsafe occlusion of theassociated tubing when conditions warrant. Fluid pressure is the basisfrom which delivered liquid volume measurements are made, from which airentrapped in the liquid is detected and elimination, and from whichoccluded liquid flow conditions are detected and diagnosed.

According to another aspect of the invention, the cassette serves toorganize and mainfold the multiple lengths of tubing and bags thatperitoneal dialysis requires. The cassette also serves to centralize allpumping and valving activities required in an automated peritonealdialysis procedure, while at the same time serving as an effectivesterility barrier.

Various features of the invention are set forth in the following claims.

We claim:
 1. A system for performing peritoneal dialysis comprisingapumping mechanism comprising a diaphragm, means for establishing flowcommunication with the patient's peritoneal cavity through the pumpingmechanism, and actuating means for emulating a selected gravity flowcondition by applying fluid pressure to the diaphragm to operate thepumping mechanism to either move dialysis solution from the peritonealcavity or move dialysis solution into the peritoneal cavity, and controlmeans selectively operating the actuating means for applying fluidpressure to emulate either a fixed head height condition or differenthead height conditions.
 2. A system according to claim 1wherein theactuating means applies pneumatic fluid pressure.
 3. A system accordingto claim 1wherein the actuating means applies fluid pressure that isbelow atmospheric pressure.
 4. A system according to claim 1wherein theactuating means applies fluid pressure that is above atmosphericpressure.
 5. A system according to claim 1wherein, in a first mode ofoperation, the actuating means applies a first magnitude of fluidpressure and, in a second mode of operation, the actuating means appliesa second magnitude of fluid pressure different than the first magnitude.6. A system according to claim 1and further including valve means fornormally isolating the patient's peritoneal cavity from the pumpingmechanism including means for selectively opening the valve means toaccommodate movement of the dialysis solution to and from the patient'speritoneal cavity.
 7. A system according to claim 6wherein the valvemeans is operated in response to fluid pressure.
 8. A system accordingto claim 6wherein the valve means is operated in response to pneumaticpressure.
 9. A peritoneal dialysis system comprisinga pumping mechanismcomprising a pump chamber, at least one valve communicating with thepump chamber, and a diaphragm, means for establishing flow communicationbetween the pumping mechanism and the patient's peritoneal cavity,actuating means for emulating gravity flow conditions by applying fluidpressure to the diaphragm to operate the pump chamber and valve to:(i)drain spent peritoneal dialysis solution from the patient's peritonealcavity, and (ii) infuse fresh dialysis solution from a source into thepatient's peritoneal cavity, and control means selectively operating theactuating means for applying fluid pressure to emulate either a fixedhead height condition or different head height conditions.
 10. A systemaccording to claim 9wherein the actuating means applies pneumatic fluidpressure.
 11. A system according to claim 9wherein the actuating meansapplies fluid pressure that is below atmospheric pressure.
 12. A systemaccording to claim 9wherein the actuating means applies fluid pressurethat is above atmospheric pressure.
 13. A system according to claim9wherein, in a first mode of operation, the actuating means applies afirst magnitude of fluid pressure and, in a second mode of operation,the actuating means applies a second magnitude of fluid pressuredifferent than the first magnitude.
 14. A peritoneal dialysis systemcomprisingmeans defining a pump chamber that has a diaphragm, patientconduit means for establishing flow communication between the pumpchamber and patient's peritoneal cavity, an other conduit means forestablishing flow communication between the pump chamber and an externalcomponent outside the patient's peritoneal cavity, means for applyingfluid pressure to the diaphragm to pump dialysis solution throughpatient conduit means and the other conduit means, and pressureregulation means for applying fluid pressure variations to the diaphragmof a first magnitude when liquid is conveyed through the patient conduitmeans and for applying fluid pressure to the diaphragm of a secondmagnitude different than the first magnitude when liquid is conveyedthrough the other conduit means.
 15. A system according to claim14wherein the first magnitude is less than the second magnitude.
 16. Asystem according to claim 14and further including means for varying themagnitudes of the pressure applied to the diaphragm to emulate differenthead height conditions.
 17. A system according to claim 14wherein theactuating means applies pneumatic pressure.
 18. A system according toclaim 14wherein the actuating means applies fluid pressure that is belowatmospheric pressure.
 19. A system according to claim 14wherein theactuating means applies fluid pressure that is above atmosphericpressure.
 20. A peritoneal dialysis system comprisingmeans defining apump chamber that has a diaphragm, conduit means for establishing flowcommunication among the patient's peritoneal cavity, a source of freshdialysis solution, and a drain through the pump chamber, actuating meansfor applying fluid pressure to the diaphragm to move spent peritonealdialysis solution from the patient's peritoneal cavity to the drainthrough the pump chamber and to pump fresh dialysis solution from thesource to the patient's peritoneal cavity through the pump chamber,means for directing fluid flow through the pump chamber includingmeansfor directing spent peritoneal dialysis solution from the patient'speritoneal cavity into the pump chamber, means for directing the spentdialysis solution from the pump chamber to the drain, means fordirecting fresh dialysis solution from the source into the pump chamber,and means for directing the fresh dialysis solution from the pumpchamber to the patient's peritoneal cavity, and pressure regulationmeans for applying fluid pressure to the diaphragm of a first magnitudewhen liquid is conveyed through the pump chamber to and from thepatient's peritoneal cavity and for applying fluid pressure variationsto the diaphragm of a second magnitude different than the firstmagnitude when liquid is conveyed through the pump chamber either to thedrain or from the source container.
 21. A system according to claim20and further including means for adjusting the magnitude of the fluidpressure variations applied to the diaphragm to emulate different headheight conditions.
 22. A system according to claim 20wherein theactuating means applies pneumatic pressure.
 23. A system according toclaim 20wherein the actuating means applies fluid pressure that is belowatmospheric pressure.
 24. A system according to claim 20wherein theactuating means applies fluid pressure that is above atmosphericpressure.
 25. A peritoneal dialysis system comprisingmeans defining apump chamber that has a diaphragm, conduit means for establishing flowcommunication among the patient's peritoneal cavity, a source of freshdialysis solution, a reservoir for heating the fresh dialysis solution,and a drain through the pump chamber, actuating means for applying fluidpressure to the diaphragm to move liquid through the pump chamber, meansfor directing liquid flow through the pump chamber includingmeans fordirecting spent peritoneal dialysis solution from the patient'speritoneal cavity into the pump chamber, means for directing the spentdialysis solution from the pump chamber to the drain, means fordirecting fresh dialysis solution from the source into the pump chamber,means for directing the fresh dialysis solution from the pump chamber tothe reservoir for heating, means for directing the heated fresh dialysissolution from the reservoir into the pump chamber, and means fordirecting the heated fresh dialysis solution from the pump chamber tothe patient's peritoneal cavity, and pressure regulation means forapplying fluid pressure to the diaphragm of a first magnitude whenliquid is conveyed through the pump chamber to and from the patient'speritoneal cavity and for applying fluid pressure to the diaphragm of asecond magnitude different than the first magnitude when liquid isconveyed through the pump chamber either to the drain; or from thesource container; or to and from the reservoir.
 26. A system accordingto claim 25and further including means for adjusting the fluid pressureapplied to the diaphragm to emulate different head height conditions.27. A system according to claim 25wherein the means for establishingflow communication includespatient conduit means for establishing flowcommunication between the pump chamber and the patient's peritonealcavity, and an other conduit means for establishing flow communicationbetween the pump chamber and a component other than the patient'speritoneal cavity, and wherein the actuator includes pressure regulationmeans for the pressure conveying means to convey fluid pressure to thediaphragm of a first magnitude when liquid is moved through the patientconduit means and to convey fluid pressure to the diaphragm of a secondmagnitude different than the first magnitude when liquid is movedthrough the other conduit means.
 28. A system according to claim27wherein the actuator includes control means for the pressure conveyingmeans operable in a first mode for conveying fluid pressure to emulate afixed head height condition.
 29. A system according to claim 28whereinthe control means is operable in a second mode for varying the magnitudeof the conveyed fluid pressure to emulate different head heightconditions.
 30. A system according to claim 27wherein the pressureconveying means conveys pneumatic pressure.
 31. A system according toclaim 27wherein the pressure conveying means conveys fluid pressure thatis below atmospheric pressure.
 32. A system according to claim 27whereinthe pressure conveying means applies fluid pressure that is aboveatmospheric pressure.
 33. A system according to claim 25wherein thefirst magnitude of fluid pressure is less than the second magnitude offluid pressure.
 34. A system for performing peritoneal dialysiscomprisinga pumping mechanism comprising a diaphragm, means forestablishing flow communication with the patient's peritoneal cavitythrough the pumping mechanism, and actuating means for emulating aselected gravity flow condition by applying pneumatic fluid pressure tothe diaphragm to operate the pumping mechanism to either move dialysissolution from the peritoneal cavity or move dialysis fluid into theperitoneal cavity, the actuating means including a chamber for receivingpneumatic pressure and insert means occupying the chamber forstabilizing the applied pneumatic pressure within the chamber.
 35. Asystem according to claim 34wherein the insert is made of an open cellporous material.